Carbon Nanotube Layer Research Articles

Preparation high quality ethanol gas sensor by modifying porous silicon (PS) surface with carbon nanotube (CNTs)

In the study, the high-quality gas sensor for ethanol was prepared by modified porous silicon (PS) with a thin layer of carbon nanotube. The PSi samples have been prepared by using the photoelectrochemical etching (PECE) process at various current densities J = 12, 24, and 30 mA/cm2 with 10 min etching time and Hydrofluoric acid concentration (HFC) of 40%. All samples (PSi and MWCNTs/PSi) were analyzed using X-ray diffraction (XRD), field emission Scanning electron microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Atomic Force Microscopic (AFM), to determine the structural, morphological, and surface bond configuration. As a result, the Photoluminescence (PL) test was performed on all samples using the PL system in order to calculate the energy band gap for all samples. Then the PSi and MWCNTs/PSi samples were applied as ethanol gas sensor at room temperature (RT). The results showed that the best sensitivity of ethanol gas was about (2.1912349) at a concentration of 500 parts per million (ppm) for MWCNTs/PSi sample compared to PSi surface, it was about (1.709) under the same used conditions at etching current density 30 mA/cm2. The MWCNTs/PSi layers serve as low-cost and high-quality ethanol gas sensors. The carbon nanotube used to replace expensive materials used in gas sensors that function at low temperatures, including room temperature. The materials have an exceptionally high surface-to-volume ratio (increasing surface area), ease of fabrication, and compatibility with silicon microelectronics manufacturing processes.

Prussian Blue/Carbon Nanotube Sensor Spread with Gelatin/Zein Glaze: A User-Friendly Modification for Stable Interference-Free H2O2 Amperometry.

We report the production and characterization of effective amperometric sensors for cathodic hydrogen peroxide (H2O2) detection. The proposed electrodes involve a combination of a H2O2-signaling Prussian Blue (PB)/carbon nanotube (CNT) layer with a glaze of the biopolymers gelatin (top) and zein (beneath) for protection against PB leakage. The sandwich-type sensor was constructed through simple "drop and dry" steps with (1) suspensions of the CNTs in a soluble PB solution, (2) zein in ethanol, and (3) gelatin in water, applied sequentially to the carbon working electrode disk of a screen-printed carbon electrode (SPCE) platform. The PB in the signaling layer acted as the electrocatalyst for H2O2 reduction at -150 mV vs Ag/AgCl/3 M KCl, enabling cathodic H2O2 amperometry with good target proportionality. Calibration trials confirmed the linearity of the response up to 700 μM (R2 > 0.998), with a sensitivity of 0.425 μA μM-1 cm-2 and a practical detection limit of 1 μM. Quantification of H2O2 in model and real samples with gelatin-zein-PB/CNT-SPCEs had a recovery of close to 100% of the true value. Since they are easily and cheaply made and yield accurate target assessments, gelatin-zein-PB/CNT-SPCEs are an ideal tool for electrochemical H2O2 analyses in human body fluids, health care products, and samples from industries that use H2O2 as a bleach and germicide. Workers with little experience in sensor fabrication and limited funding will particularly benefit from utilization of the proposed H2O2 probes, which as well as being used in H2O2 testing also have a potential application as the transducer unit of oxidase-based biosensors with amperometric H2O2 readout.

Cryogenic-environment resistant, highly elastic hybrid carbon foams for pressure sensing and electromagnetic interference shielding

Elastic carbon foams are promising material candidates for various applications, including strain/pressure sensing and electromagnetic interference (EMI) shielding, but typically suffer from brittleness, low sensitivity, narrow pressure detection range, and poor performance stability. Herein, a facile and scalable method was demonstrated to fabricate carbon nanotube (CNT) embedded carbonized melamine foams (CNT/CMFs) by a direct pyrolysis process. The hybrid CNT/CMFs show tunable electrical conductivity while providing ultrahigh elasticity even under deep cryogenic conditions (−196 °C). An ultrahigh sensitivity (up to 103.24 kPa−1) and a broad pressure detection range (0–175 kPa) were achieved by the hybrid foam sensors, attributing to the hierarchical structures composed of a nanofibrous CNT layer and macropores. The foam-based sensors exhibit ultrahigh cryogenic-temperature resistance, which retains stable performance after immersing in liquid nitrogen for 36 h and experiencing 5000 cycles of repeated compression-release. Moreover, the CNT/CMFs show an exceptional EMI shielding effectiveness and a high specific shielding effectiveness of 6147.3 dB cm2 g−1 with an absorption-dominant shielding mechanism due to the highly porous structure. The cryogenic-temperature resistant CNT/CMFs with these superior strain/pressure sensing and EMI shielding performance are promising for their practical applications as wearable electronics operating in both mild and harsh environments.

Polarization-dependent conversion efficiency of carbon nanotube-Si heterojunction solar cells based on aligned carbon nanotube films

We have fabricated solar cells that implement heterojunctions of Si and aligned carbon nanotube (CNT) films. Polarization-dependent optical absorption of highly aligned CNTs led to polarization-dependent conversion efficiencies, which in turn provided insight into the role of the CNT layer in the power generation mechanism in these heterojunction solar cells. When the incident light polarization was parallel to the CNT alignment direction so that the light absorption in the CNT layer was maximized, the short circuit photocurrent decreased by ∼25%. This indicates that electron–hole pair generation in the CNT layer does not directly lead to power generation and that the CNT-Si heterojunctions in our devices are Schottky junctions rather than p–n junctions.

Polyester fabric impregnated with carbon nanotubes directly to form a flexible heating fabric

In order to solve the problems of complex fabrication process, poor flexibility and high cost of heating element in electric heating clothing, a method of preparing flexible heating fabric by directly impregnating polyester fabric with carbon nanotube was proposed. According to the process flow of preparing flexible heating fabric, the process conditions of uniform loading carbon nanotubes on polyester fabric were determined, the flexible heating fabric was prepared under different process conditions, and the surface microstructure of the flexible heating fabric was observed and its heating performance was tested. The results show that the pretreatment process can reduce the resistance value of the flexible heating fabric. When the concentration of carbon nanotubes is 6wt% and the content of waterborne polyurethane is 35g/L, the flexible heating fabric can be prepared. By observing the surface micro-topography, it can be seen that the surface of the prepared flexible heating fabric is smooth, and a uniform conductive layer of carbon nanotubes is formed on the fabric. A 5V DC voltage was applied to the prepared flexible heating fabric, and the highest heating temperature was 46.8°C within 62 seconds after the electricity was turned on, which realized rapid electric heating and uniform heating, laying a foundation for the subsequent development of heating clothing.

Conductive reverse osmosis membrane for electrochemical chlorine reduction and sustainable brackish water treatment

The susceptibility of RO membrane for chlorine, which is widely used for disinfecting the feedwater, remains a biggest challenge. Herein for the first time, we report an electrochemical chlorine reduction on a conductive RO membrane interface as a sustainable solution to overcome this limitation. In this study, cyclic voltammetry was employed to investigate the potential of electrochemical chlorine reduction. Later, a conductive RO membrane with an embedded carbon nanotubes layer (CNT-RO) was fabricated, and its resistance to chlorine was tested via batch soaking into a sodium hypochlorite solution (NaOCl; 1,000 ppm; pH = 5) used as the chlorine source, followed by the flux and salt rejection monitoring.The CNT-RO membrane resulted in 3.5% and 9.3% chlorine uptake after chlorinating for 1 h and 24 h, hence faced prominent decline in the amide II and aromatic amide peak positioned at 1541 cm−1 and 1609 cm−1, respectively. In contrast, the application of 2 V on conductive CNT-RO membrane interface when used as a cathode resulted in an irreversible chlorine reduction, hence formed chloride as validated via ion chromatography. Chlorination of CNT-RO membrane under conducting mode could not cause any significant change in the membrane morphology, elemental composition, amide bonding structure, and surface wettability. Therefore, CNT-RO membrane demonstrated 88% rejection against monovalent salt even after 24 h of chlorination under conducting mode as compared to the commercial and CNT-RO (chlorinated without DC charge application) which showed 69% and 74% rejection, respectively. These findings clearly illustrated the potential of conductive RO membrane for sustainable desalination and water reuse applications.

High-Resolution R2R-Compatible Printing of Carbon Nanotube Conductive Patterns Enabled by Cellulose Nanocrystals

Carbon nanotubes (CNTs) with enhanced properties compared to conventional materials are a leading material of choice for fabricating next-generation electronic devices. Nanocellulose-based conductive component-enabled electronics also offer great potential for commercial scalability of environmentally friendly, sustainable, flexible, wearable electronics. Printing these functional materials through R2R printing will enable the economic and high-throughput production of next-generation electronic devices. However, the lateral resolution during R2R printing of these materials is currently limited due to the enhanced aggregation behavior of these high-aspect ratio particles, and the lower lateral resolution limits the performance of the fabricated devices. This article demonstrates high-resolution, R2R-compatible printing of conductive patterns of CNTs using cellulose nanocrystals (CNCs) through the topographical discontinuous dewetting and liquid-bridge transfer patterning technique. The CNC dispersion obtained through acid hydrolysis of spinifex grass biomass was used as a sustainable functional ink and deposited as a structural wetting layer, which necessarily allowed the subsequent deposition of a conductive CNT layer to form high-resolution conductive patterns. Conductive patterns with lateral feature sizes down to ∼4.5 μm were reliably printed and those with feature sizes down to ∼925 nm were also possible. The high-resolution conductive CNC/CNT patterns could be printed on different hydrophilic substrates, including flexible, transparent CNC films, for use in devices. This study represents a proof-of-concept for the realization of the economic and environmentally friendly printing of high-resolution nanocellulose/carbon-based electronics.

Carbon‐based light‐induced thermoelastic spectroscopy for ammonia gas sensing

AbstractA light‐induced thermoelastic spectroscopy (LITES) based on carbon nanotubes (CNT), graphene oxide (GO), and reduced graphene oxide (rGO) coated quartz tuning fork (QTF) was proposed. In order to improve the conversion efficiency of laser energy radiation into the vibration of tuning fork, thin CNT, GO, and rGO layers were coated on the surface of commercial QTF, respectively. Ammonia (NH3) gas was selected as the target analyte for the experimental validation. The experimental results show that the system's maximum gain factor in signal amplitude and signal‐to‐noise ratio (SNR) are 1.52, 1.53, 2.43, and 1.54, 1.33, 2.24 times, respectively, as compared with the traditional LITES with bare QTF.

Improvement of the Sensitivity and Selectivity of Gas Molecules of Graphene-base Gas Sensor by Applying Carbon Nanotubes

Chemical biosensors using graphene as a sensing element have been developed for a new generation of highly-sensitive miniature exhaled multi-gas sensors for early detection of various diseases. In this study, carbon nanotubes (CNTs) were synthesized directly on graphene to increase the surface area of the molecular adsorption in order to improve the sensitivity and selectivity of the graphene-based gas sensor. The synthesis of graphene was performed in a low-pressure chemical vapor deposition apparatus on a very pure copper catalyst substrate. The grown graphene was transferred onto a Si/SiO2 substrate. A CNT layer was also formed directly on the graphene sensor element using a thermochemical vapor deposition method. Stable ohmic contact was observed between the synthesized CNTs and the base graphene layer. It was also confirmed that the sensitivity of the graphene sensor with the CNT layer to gas molecules was improved by about 4 times compared with the conventional graphene sensor.

Fully handwritten electrodes on paper substrate using rollerball pen with silver nanoparticle ink, marker pen with carbon nanotube ink and graphite pencil.

Herein, a so-called carbon nanotube (CNT) electrode was printed in on a paper substrate using the handwriting technique and carbon nanotube ink in a marker pen to print the working electrode, graphite pencil to print the counter electrode and graphite/silver nanoparticle (AgNP) ink in a rollerball pen to print the quasi-reference electrode. The carbon nanotube electrode was characterized via scanning electron microscopy. The electrode was optimized based on the type of paper, hydrophobic barrier and number of layers. In summary, the optimized parameters included the use of matte paper with a mineral spirit layer. The number of carbon nanotube layers to achieve the best electrochemical performance was 25. The final graphite electrode was a miniaturized and flexible paper-based electrochemical electrode. To evaluate the electrical properties of the electrodes, the ohmic resistance of each ink was tested using a multimeter and the obtained values were 18.62 kΩ for the CNT ink, 1.53 Ω for the AgNP ink and 3.53 kΩ for the graphite trace. These results indicate the good conductivity of each synthesized ink used in the fabrication of the CNT electrode. Finally, the electrode was used to measure the electrochemical response of different concentrations of K4[Fe(CN)6]. Then, a calibration curve was obtained from the voltammograms and linearity was observed in the range of 0.5-3.5 mM. This suggests that the CNT electrode has the potential to be used as an amperometric electrode.

Electrochemical Improvement of the MWCNT/Al Electrodes for Supercapacitors.

An original technique of chemical deposition (CVD) by catalytic pyrolysis of ethanol vapor was used to directly grow multiwall carbon nanotubes (MWCNTs) layers on aluminum foil. The grown nanotubes had excellent adhesion and direct electrical contact to the aluminum substrate. This material was perfect for use in electrochemical supercapacitors. In this work, the possibility of a significant increase in the specific capacity of MWCNTs by simple electrochemical oxidation was investigated. The optimal conditions for improving the characteristics of the MWCNT/Al electrodes were found. Electrochemical treatment of MWCNT/Al electrodes in a 0.005 M Na2SO4 solution at a potential of 4–5 V for 20–30 min increased the specific capacity of MWCNTs from 30 F/g to 140 F/g. The properties of modified nanotubes were investigated by X-ray photoelectron spectroscopy, cyclic voltammetry (CV), and impedance spectroscopy. A significant increase in the concentration of oxygen-containing functional groups on the surface of MWCNTs was found as a result of electrochemical oxidation. The modified MWCNT/Al electrodes maintained excellent stability to multiple charge–discharge cycles. After 20,000 CVs, the capacity loss was less than 5%. Thus, the results obtained significantly expanded the possibilities of using MWCNT/Al composite materials obtained by the method of direct deposition of carbon nanotubes on aluminum foil as electrodes for supercapacitors.

Novel designed electrochemical sensor for simultaneous determination of linezolid and meropenem pneumonia drugs

• Layer by layer method is applied to fabricate GC/Gr/CNT-HQ/Fe-Ni sensor for electrochemical determination of LN and ME in human blood serum. • Practically determination of LN and ME in human serum is successfully accomplished in a wide concentration ranges with low detection limits of 0.97 nM and 1.3 nM respectively. • The sensor can efficiently be used for concurrent determination of three antibiotic drugs namely LN, ME, and TH in human serum. • Excellent interference resistance, good reproducibility and perfect storage stability are the features of the GC/Gr/CNT-HQ/Fe-Ni sensor. Treatment of pneumonia by only one antibiotic drug is difficult due to the involvement of several microorganisms in pneumonia disease as Methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella. Thus introducing another antibiotic drug meropenem (ME) beside the linezolid (LN) are usually used for treatment of pneumonia cases. Layer by layer method is applied to fabricate sensor for electrochemical determination of LN and ME in human blood serum. A glassy carbon surface (GC) is modified with a thin layer of graphene (Gr) followed by casting two consecutive thin layers of carbon nanotubes- hydroquinone mixture (CNT-HQ) and Fe-Ni alloy nanoparticles; GC/Gr/CNT-HQ/Fe-Ni. The current signals enhancement is due to the synergism of all the sensor components. Voltammetry determination of LN and ME in human serum is successfully accomplished in the concentration ranges (0.007–12 µM) and (0.01–12 µM) with low detection limits of 0.97 nM and 1.3 nM, respectively. Also, the sensor can efficiently be used for concurrent determination of three antibiotic drugs namely LN, ME and theophylline (TH) in human serum. The GC/Gr/CNT-HQ/Fe-Ni sensor is practically used in human serum samples for LN and ME determination with satisfactory recoveries, outstanding interference resistance and good stability.

Spray deposited thin uniform NiO/Spiro-OMeTAD composite hole transport layer with top carbon nanotube electrode

Thin Spiro-OMeTAD and NiO nanoparticles layers, as well as their composite layer was formed by layer-by-layer spray deposition as hole-transport layer (HTL), with followed carbon nanotubes (CNT) deposition to form Ti/TiO2/HTL/CNT structures. Layers’ uniformity was estimated by Raman intensity maps, AFM and current-voltage characteristics of the CNT layer and between CNT and Ti contacts. The possibility of formation of thin, less than 100 nm, pinhole-free uniform composite NiO/Spiro-OMeTAD layer by spray-deposition was shown, which manifests itself as continuous HTL even after top CNT layer deposition.

A highly stable, nanotube-enhanced, CMOS-MEMS thermal emitter for mid-IR gas sensing

The gas sensor market is growing fast, driven by many socioeconomic and industrial factors. Mid-infrared (MIR) gas sensors offer excellent performance for an increasing number of sensing applications in healthcare, smart homes, and the automotive sector. Having access to low-cost, miniaturized, energy efficient light sources is of critical importance for the monolithic integration of MIR sensors. Here, we present an on-chip broadband thermal MIR source fabricated by combining a complementary metal oxide semiconductor (CMOS) micro-hotplate with a dielectric-encapsulated carbon nanotube (CNT) blackbody layer. The micro-hotplate was used during fabrication as a micro-reactor to facilitate high temperature (>700 ^{circ }C) growth of the CNT layer and also for post-growth thermal annealing. We demonstrate, for the first time, stable extended operation in air of devices with a dielectric-encapsulated CNT layer at heater temperatures above 600 ^{circ }C. The demonstrated devices exhibit almost unitary emissivity across the entire MIR spectrum, offering an ideal solution for low-cost, highly-integrated MIR spectroscopy for the Internet of Things.

Flexible Electrode Formed by Patterned Layers of Single-Walled Carbon Nanotubes for Optoelectronic Applications

The technology of creating patterned flexible electrodes based on single-walled carbon nanotubes and polydimethylsiloxane was demonstrated in this paper. A series of experiments were carried out to study whether the percolation affects the conductivity of patterned SWCNT layers. It was found that in patterns with the linewidth above 1 μm and the cell size above 50 μm the random character of SWCNT networks may be neglected. The impact of bending on the grid conductivity was studied. We observed a very moderate increase of resistance below 5% under the strain up to 4 %, which is comparable with the previous results for continuous SWCNT layers and shows the improvement in comparison with the previous reports on patterned SWCNT layers.

Absolute and Fast Removal of Viruses and Bacteria from Water by Spraying-Assembled Carbon-Nanotube Membranes.

Membrane separation is able to efficiently remove pathogens like bacteria and viruses from water based on size exclusion. However, absolute and fast removal of pathogens requires highly permeable but selective membranes. Herein, we report the preparation of such advanced membranes using carbon nanotubes (CNTs) as one-dimensional building blocks. We first disperse CNTs with the help of an amphiphilic block copolymer, poly(2-dimethylaminoethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS, abbreviated as BCP). The PS blocks adsorb on the surface of CNTs via the π-π interaction, while the PDMAEMA blocks are solvated, thus forming homogeneous and stable CNT dispersions. We then spray the CNT dispersions on porous substrates, producing composite membranes with assembled CNT layers as the selective layers. We demonstrate that the optimized membrane shows 100% rejection to phage viruses and bacteria (Escherichia coli) while giving a water permeance up to ∼3300 L m-2 h-1 bar-1. The performance of the resultant BCP/CNT membrane outperforms that of state-of-the-art membranes and commercial membranes. The BCP/CNT membrane can be used for multiple runs and regenerated by water rinsing. Membrane modules assembled from large-area membrane sheets sustain the capability of absolute and fast removal of viruses and bacteria.

High Efficient Ion Selective Membrane Separator for Room Temperature Sodium Polysulfide Redox Flow Batteries

Redox flow batteries (RFBs) have attracted extensive attention in recent years due to their low cost, safe operation, and design flexibility for large scale energy storage applications. Among various types of high-energy-density candidates, lithium-polysulfide (LiPS) and the NaPS equivalent RFBs are especially attractive due to their high energy density and natural abundance of sulfur, which can significantly decrease the capital cost of the RFB system to metrics suitable for deep market penetration. Owing to the lower cost of Na than Li, NaPS RFBs will be able to offer more advantageous for large grid-scale energy storage system applications. Although a molten electrode-based NaS RFB has been successfully developed to support stationary energy storage systems, its high operation temperatures (> 250 °C) and the use of ceramic ion conductors (e.g., beta-alumina solid electrolytes) cause safety and high-cost concerns. To overcome the limitations of high-temperature NaS battery, room temperature NaPS (RT-NaPS) batteries emerged as alternatives. However, the current status of RT-NaPS RFB have to overcome several issues associated with deleterious self-discharge and high rate of capacity-fade. These two macroscopic challenges are fundamentally underpinned by the crossover of polysulfide (PS), so-called shuttle effect, during cycling. Although ceramic conductors (e.g., NASICON) show promising ion selectivity, their fragile mechanical properties and high cost pose major drawbacks for broader application in RFBs. Celgard®, the most widely adopted porous membrane for the LIBs, are highly permeable to PS ions, thus it is not suitable as a separator for NaPS RFBs. The use of Nafion, an ion selective membrane (ISM), in NaPS RFB improved discharge capacity and cycle stability compared to Celgard (350 mAh/g vs. 200 mAh/g at 20 cycles). However, Nafion cannot achieve good performance in organic phase of Na-PS RFBs due to the persistently high crossover of redox couples caused by swelling of the perfluorinated membrane in organic electrolytes.Here we present a multifunctional electrochemical nanocomposite membrane (mECM) with excellent polysulfide blocking properties and chemical stability in organic electrolytes. A biphenyl backbone-based aromatic hydrocarbon membrane reinforced by porous carbon nanotubes layer and boron nitride nanotube layer shows high sodium conductivity as well as sodium selectivity over PS. Our mECM greatly reduce PS crossover which is lower than commercial Celgard 2325 by 4-order of magnitude, while areal resistance is only 3 times higher than Celgard 2325 (25.10 Ω cm2 vs. 7.6 Ω cm2). As a result, the performance of the Na-PS RFB single cell with our composite membranes is superior to that of Celgard and other commercial IEMs (e.g. Nafion 215) under the same condition. The capacity decay rate of the Na-PS RFB cell with the mECM is significantly lower than that of Celgard 2325, which is largely attributed to the excellent capability of mECM to suppress PS crossover. After 200 charge/discharge cycle, the Na-PS cell with Celgard 2325 lost 70% of its initial capacity (initial 1000 mAh/g to 300 mAh/g); in contrast, the Na-PS cell with the mECM achieved 81% capacity retention (initial 900 mAh/g to 750 mAh/g), demonstrating the possibility of our membrane to use in long-term operation of RT-NaPS RFB (Fig. a). Our results show that the performance of our RT-NaPS cell (Fig. b) outperforms other RT-NaS cells reported so far. More detailed descriptions of ion transport properties, electrochemical properties, and battery performance of the membrane separators will be presented. Figure 1

Polymer Blends and Polymer Nanocomposites for Photovoltaic (PV) Cells and an Investigation of the Material Deposition Techniques in PV Cell Fabrication

Polymer photovoltaics (PV) offer the advantage of low-cost, mass-produced, flexible PV films, but they generally suffer from a low-power conversion efficiency (PCE) compared to silicon. This paper studies ITO/PEDOT:PSS/bulk heterojunction/Al PV cells, where two different bulk heterojunction blends are researched: P3HT/PC61BM and PCDTBT/PC70BM. The addition of multiwall carbon nanotubes (CNT) is explored as a conductive network to accelerate the electron transport and extraction to the outer aluminium current collector while reducing the chance of charge recombinations. Several layer deposition techniques are investigated: spin coating and casting, as well as techniques that would induce transverse orientation of polymer grains, including inkjet printing, electrophoresis and the application of a transverse AC field during annealing. Transverse orientation techniques produced architectures that would facilitate charge transport without recombinations, but it is recommended to avoid such techniques for the deposition of conductive PEDOT:PSS and CNT layers as they create a high surface roughness that leads to short circuiting. The best performing PV cell is the ITO/PEDOT:PSS/PCDTBT/PC70BM/CNT/Al structure with a PCE of 11%.

Synthesis and characterization of carbon nanotube doped with zinc oxide nanoparticles CNTs-ZnO/PS as ethanol gas sensor

Nanocomposites have the potential to produce very selective, stable, and sensitive sensors. Nanocomposites porous structures have a larger surface area for gas molecule adsorption. In this paper, the high quality gas sensor was prepared by modified porous layer of silicon (PS) with a thin layer of carbon nanotube (CNTs) and carbon nanotube doped with zinc oxide (ZnO) nanoparticles (70–30)% respectively. PS samples were created using the photoelectrochemical etching method (PECE), for N-type silicon (Si) wafer with resistivity of (1.5–4) Ω cm and a thickness (580 ± 0.25) μm. Three etching current densities were employed for prepare PS layers 12, 24, and 30 mA/cm2, while, the hydrofluoric acid HFc concentration of 40% and etching time was about 10 min. The Structure characteristics, morphological features, and surface chemical bond formation of all PS and (MWCNTs-ZnO/PS) samples were examined using X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and Transition Electron Microscope (TEM). All PS and MWCNTs-ZnO/PS samples were applied as ethanol gas sensors at room temperature. The results revealed that CNTs-ZnO/PS had the highest sensitivity to ethanol gas at etching current density 30 mA/cm2, reaching about (2.004984) at a concentration of 500 ppm. Fusion of CNTs-ZnO leads to the emergence of new properties and unique effects, and as a result of the excellent sensing ability of carbon nanotubes in detecting different gases at room temperature, Used in the manufacture of highly selective gas sensors that operate at room temperature. The Interest of this article return to study the effect of extremely high surface to volume ratio (increasing surface area), and ease composition and compatibility with modern silicon microelectronics manufacturing technologies.

Development of a sensitive voltammetric sensor for diltiazem determination in biological samples using MWCNT/PPy-PBA modified glassy carbon electrode

A glassy carbon (GC) electrode was modified for diltiazem determination in various samples using the cyclic voltammetry (CV) method. The modification consists of coating a multi-walled carbon nanotubes (MWCNTs) layer on the GC electrode, which is followed by electro-polymerization of pyrrole in the presence of phenylboronic acid (PBA). The experimental design was used to find optimum experimental conditions for electrode fabrication and diltiazem determination. Under optimum conditions, the calibration curve of diltiazem is linear in 0.25–2 μmol/L and 2–80 μmol/L ranges with a detection limit of (LOD) 7.1 × 10−8 mol/L. Further application of the GC/MWCNT/PPy-PBA electrochemical sensor for diltiazem determination shows good reproducibility, high sensitivity, and reasonable selectivity with no major interference. These characteristics make the sensor suitable for the determination of diltiazem in biological and pharmaceutical samples. To rationalize the modification on the electrochemical behavior of the sensor regarding diltiazem, geometrical interaction and interaction energy of the analyte with the sensor surface were investigated using highly accurate quantum mechanical methods implemented in Gaussian 09 software. The calculations fully confirm experimental evidence.