Investigation of the electrochemical and electrocatalytic behavior of single-wall carbon nanotube film on a glassy carbon electrode

Controlled Chemical Vapor Deposition and Modification of Carbon Layers inside Quartz Nanopipettes

Carbon nanopipettes (CNPs) have attracted much attention in nanoscale electrochemical applications recently, while the carbon structure and surface oxygen-containing groups limit its applications. Herein, we grow the carbon nanotubes (CNTs) inside the quartz nanopipet via the chemical vapor deposition method, and the fabricated carbon nanotube nanopipettes (CNT-NPs) exhibit better electrochemical responses toward biomolecules such as glutathione and ascorbic acid, compared to the conventional CNPs. In addition, the carbon nanopipette can also be easily doped by a chemical reaction with urea, to display positive surface charges and high electrochemical activity for H2O2 oxidation/reduction. This work provides an easy way to tailor the surface structure and charges of the deposited carbon inside the pipettes and thus would further promote its broader usage in electrochemical sensing applications in biological fields.

Electrochemical sensing fibers for wearable health monitoring devices

Real-time monitoring of health conditions is an emerging strong issue in health care, internet information, and other strongly evolving areas. Wearable electronics are versatile platforms for non-invasive sensing. Among a variety of wearable device principles, fiber electronics represent cutting-edge development of flexible electronics. Enabled by electrochemical sensing, fiber electronics have found a wide range of applications, providing new opportunities for real-time monitoring of health conditions by daily wearing, and electrochemical fiber sensors as explored in the present report are a promising emerging field. In consideration of the key challenges and corresponding solutions for electrochemical sensing fibers, we offer here a timely and comprehensive review. We discuss the principles and advantages of electrochemical sensing fibers and fabrics. Our review also highlights the importance of electrochemical sensing fibers in the fabrication of "smart" fabric designs, focusing on strategies to address key issues in fiber-based electrochemical sensors, and we provide an overview of smart clothing systems and their cutting-edge applications in therapeutic care. Our report offers a comprehensive overview of current developments in electrochemical sensing fibers to researchers in the fields of wearables, flexible electronics, and electrochemical sensing, stimulating forthcoming development of next-generation "smart" fabrics-based electrochemical sensing.

Fouling-resistant electrode for electrochemical sensing based on covalent-organic frameworks TpPA-1 dispersed cabon nanotubes

The key problem that limits the practical applications of nonenzymatic electrochemical sensors in biological media, is the biofouling and chemical fouling of electrodes due to the adsorption of biological molecules and oxidation (reduction) products. Electrode fouling will cause low accuracy, poor stability, and low sensitivity. Here, a simple and efficient antifouling electrode was demonstrated for electrochemical sensing based on covalent-organic framework (COF) TpPA-1 and carboxylic multi-walled carbon nanotubes (CNT) composites. COF TpPA-1 possesses abundant hydrophilic groups, which assisted the dispersion of CNT in water and formed uniform composites by π-π interaction. In addition, the introduction of CNT into the composites improved the electron transfer rate of COF TpPA-1. The antifouling interface was characterized by electrochemistry, contact angle measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The electrode showed good chemical and bio-fouling resistant performance for the electrochemical detection of β-nicotinamide adenine dinucleotide (NADH) and uric acid (UA) in real serum samples.

Optimum Choice of Randomly Oriented Carbon Nanotube Networks for UV-Assisted Gas Sensing Applications

We investigated the noise and photoresponse characteristics of various optical transparencies of nanotube networks to identify an optimal randomly oriented network of carbon nanotube (CNT)-based devices for UV-assisted gas sensing applications. Our investigation reveals that all of the studied devices demonstrate negative photoconductivity upon exposure to UV light. Our studies confirm the effect of UV irradiation on the electrical properties of CNT networks and the increased photoresponse with decreasing UV light wavelength. We also extend our analysis to explore the low-frequency noise properties of different nanotube network transparencies. Our findings indicate that devices with higher nanotube network transparencies exhibit lower noise levels. We conduct additional measurements of noise and resistance in an ethanol and acetone gas environment, demonstrating the high sensitivity of higher-transparent (lower-density) nanotube networks. Overall, our results indicate that lower-density nanotube networks hold significant promise as a viable choice for UV-assisted gas sensing applications.

A Planar Disk Electrode Chip Based on MWCNT/CS/Pb2+ Ionophore IV Nanomaterial Membrane for Trace Level Pb2+ Detection

Unlike conventional lead ion (Pb2+) detecting methods, electrochemical methods have the attractive advantages of rapid response, good portability and high sensitivity. In this paper, a planar disk electrode modified by multiwalled carbon nanotube (MWCNTs)/chitosan (CS)/lead (Pb2+) ionophore IV nanomaterial and its matched system are proposed. This system presented a good linear relationship between the concentration of Pb2+ ions and the peak current in differential pulse stripping voltammetry (DPSV), under optimized conditions of -0.8 V deposition potential, 5.5 pH value, 240 s deposition time, performed sensitive detection of Pb2+ within sensitivity of 1.811 μA · μg^-1 and detection limit of 0.08 μg · L^-1. Meanwhile, the results of the system in detecting lead ions in real seawater samples are highly similar to that of inductively coupled plasma emission spectrometer (ICP-MS), which proved a practicability for the system in detection of trace-level Pb2+.

Water Quality Carbon Nanotube-Based Sensors Technological Barriers and Late Research Trends: A Bibliometric Analysis

Water is the key element that defines and individualizes our planet. Relative to body weight, water represents 70% or more for the majority of all species on Earth. Taking care of water as a whole is equivalent with taking care of the entire biodiversity or the whole of humanity itself. Water quality is becoming an increasingly important component of terrestrial life, hence intensive work is being conducted to develop sensors for detecting contaminants and assessing water quality and characteristics. Our bibliometric analysis is focused on water quality sensors based on carbon nanotubes and highlights the most important objectives and achievements of researchers in recent years. Due to important measurement characteristics such as sensitivity and selectivity, or low detection limit and linearity, up to the ability to measure water properties, including detection of heavy metal content or the presence of persistent organic compounds, carbon nanotube (CNT) sensors, taking advantage of available nanotechnologies, are becoming increasingly attractive. The conducted bibliometric analysis creates a visual, more efficient keystones mapping. CNT sensors can be integrated into an inexpensive real-time monitoring data acquisition system as an alternative for classical expensive and time-consuming offline water quality monitoring. The conducted bibliometric analysis reveals all connections and maps all the results in this water quality CNT sensors research field and gives a perspective on the approached methods on this specific type of sensor. Finally, challenges related to integration of other trends that have been used and proven to be valuable in the field of other sensor types and capable to contribute to the development (and outlook) for future new configurations that will undoubtedly emerge are presented.

IoT-Enabled Integrated Smart Wound Sensor for Multiplexed Monitoring of Inflammatory Biomarkers at the Wound Site

Chronic wounds that stall at the inflammatory phase of healing may create several life-threatening complications such as tissue damage, septicemia, and organ failures. In order to prevent these adverse clinical outcomes and accelerate the wound healing process, it is crucial to monitor the wound status in real-time so that immediate therapeutic interventions can be implemented. In addition, continuous monitoring of the wound status can prevent drug overdose at the wound site, leading to on-demand and personalized drug delivery. Inflammatory mediators, such as Interleukin-6 (IL-6) and Interleukin-10 (IL-10) are promising indicators for the progression of wound healing and predictors of disease severity. Toward this end, this work reports a flexible wound patch for multiplexed monitoring of IL-6 and IL-10 at the wound site in order to provide real-time feedback on the inflammation phase of the wound. An optimized composition of gold nanoparticles integrated multiwalled carbon nanotube was demonstrated to improve sensor performance substantially. The sensor also exhibited excellent repeatable, reversible, and drift characteristics. A miniaturized Internet-of-things (IoT)-enabled potentiostat was also developed and integrated with the flexible sensor to realize a wearable system. This IoT-enabled wearable device provides a smart and cost-effective solution to improving the existing wound care through continuous, real-time, and in-situ monitoring of multiple wound biomarkers.

Bimetallic nickel/manganese phosphate–carbon nanofiber electrocatalyst for the oxidation of formaldehyde in alkaline medium

The development of earth-abundant transition metal-based catalysts, supported by a conductive carbonaceous matrix, has received great attention in the field of conversion of formaldehyde derivatives into toxic-free species. Herein, we report a comprehensive investigation of bimetallic electrocatalyst activity towards the electrooxidation of formaldehyde. The bimetallic phosphate catalyst is prepared by co-precipitation of Ni and Mn phosphate precursors using a simple reflux approach. Then the bimetallic catalyst is produced by mixing the Ni/Mn with carbon fibres (CNFs). The structural properties and crystallinity of the catalyst were investigated by using several techniques, such as scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Brunauer Emmett−Teller theory. The system performance was studied under potentiostatic conditions. Some theoretical thermodynamic and kinetic models were applied to assess the system performance. Accordingly, key electrochemical parameters, including surface coverage (Γ) of active species, charge transfer rate (k_s), diffusion coefficient of the formaldehyde (D), and catalytic rate constant (k_cat) were calculated at Γ = 1.690 × 10⁻⁴ mmol cm⁻², k_s = 1.0800 s⁻¹, D = 1.185 × 10⁻³ cm² s⁻¹ and k_cat = 1.08 × 10⁵ cm³ mol⁻¹ s⁻¹. These findings demonstrate the intrinsic electrocatalytic activity of formaldehyde electrooxidation on nickel/manganese phosphate- CNFs in alkaline medium.

The catalytic performance of bimetallic Ni/Mn phosphate–carbon nanofiber composite catalyst is better than mono metallic catalysts toward electrooxidation of formaldehyde.

Electrical and Electrochemical Sensors Based on Carbon Nanotubes for the Monitoring of Chemicals in Water-A Review

Carbon nanotubes (CNTs) combine high electrical conductivity with high surface area and chemical stability, which makes them very promising for chemical sensing. While water quality monitoring has particularly strong societal and environmental impacts, a lot of critical sensing needs remain unmet by commercial technologies. In the present review, we show across 20 water monitoring analytes and 90 references that carbon nanotube-based electrochemical sensors, chemistors and field-effect transistors (chemFET) can meet these needs. A set of 126 additional references provide context and supporting information. After introducing water quality monitoring challenges, the general operation and fabrication principles of CNT water quality sensors are summarized. They are sorted by target analytes (pH, micronutrients and metal ions, nitrogen, hardness, dissolved oxygen, disinfectants, sulfur and miscellaneous) and compared in terms of performances (limit of detection, sensitivity and detection range) and functionalization strategies. For each analyte, the references with best performances are discussed. Overall, the most frequently investigated analytes are H+ (pH) and lead (with 18% of references each), then cadmium (14%) and nitrite (11%). Micronutrients and toxic metals cover 40% of all references. Electrochemical sensors (73%) have been more investigated than chemistors (14%) or FETs (12%). Limits of detection in the ppt range have been reached, for instance Cu(II) detection with a liquid-gated chemFET using SWCNT functionalized with peptide-enhanced polyaniline or Pb(II) detection with stripping voltammetry using MWCNT functionalized with ionic liquid-dithizone based bucky-gel. The large majority of reports address functionalized CNTs (82%) instead of pristine or carboxyl-functionalized CNTs. For analytes where comparison is possible, FET-based and electrochemical transduction yield better performances than chemistors (Cu(II), Hg(II), Ca(II), H2O2); non-functionalized CNTs may yield better performances than functionalized ones (Zn(II), pH and chlorine).

Biosensors and nanotechnology for cancer diagnosis (lung and bronchus, breast, prostate, and colon): a systematic review

The second cause of death in the world has been reported to be cancer, and it has been on the rise in recent years. As a result of the difficulties of cancer detection and its treatment, the survival rate of patients is unclear. The early detection of cancer is an important issue for its therapy. Cancer detection based on biomarkers may effectively enhance the early detection and subsequent treatment. Nanomaterial-based nanobiosensors for cancer biomarkers are excellent tools for the molecular detection and diagnosis of disease. This review reports the latest advancement and attainment in applying nanoparticles to the detection of cancer biomarkers. In this paper, the recent advances in the application of common nanomaterials like graphene, carbon nanotubes, Au, Ag, Pt, and Fe₃O₄together with newly emerged nanoparticles such as quantum dots, upconversion nanoparticles, inorganics (ZnO, MoS₂), and metal-organic frameworks for the diagnosis of biomarkers related to lung, prostate, breast, and colon cancer are highlighted. Finally, the challenges, outlook, and closing remarks are given.

Construction of all-carbon micro/nanoscale interconnected sulfur host for high-rate and ultra-stable lithium-sulfur batteries: Role of oxygen-containing functional groups

Carbon nanotubes (CNTs) are often used to settle down the sluggish reaction kinetics in lithium-sulfur batteries (LSBs). However, the self-aggregation of CNTs often makes them fail to effectively inhibit the shuttling effect of soluble lithium polysulfide (LiPS) intermediates. Herein, a type of ultra-stable carbon micro/nano-scale interconnected "carbon cages" has been designed by incorporating polar acid-treated carbon fibers (ACF) into three-dimensional (3D) CNT frameworks during vacuum filtration processes. Results show that the ACF-CNT composite frameworks possess a reinforced-concrete-like structure, in which the ACFs can well work as the main mechanical supporting frames for the composite electrodes, and the oxygen-containing functional groups (OFGs) formed on them as cross linker between ACFs and CNTs. Benefitted from this design, the ACF-CNT/S cathodes deliver an excellent rate capability (retain 72.6% at 4C). More impressively, the ACF-CNT/S cathodes also show an ultrahigh cycling stability (capacity decay rate of 0.001% per cycle over 350 cycles at 2C). And further optimization suggests that the suitable treatment on CFs could balance the chemical adsorption (OFGs) and physical confinement (carbon cages), leading to fast and durable electrochemical reaction dynamics. In addition, the assembled soft-pack LSBs further show a high dynamic bending stability.

One-step hydrothermal method for preparation of Ni/carbon thin film electrodes for efficient electroreduction of imidacloprid

A Ni/CTF was used as the cathode for electroreduction of imidacloprid, achieving a 92.1% removal efficiency for the electroreduction of imidacloprid.

Structural mechanism of reactivation with steam of pitch-based activated carbon fibers

Customized micro- and mesoporous carbons are in high demand for ecofriendly technologies. Reactivation of the well-characterized pitch-based activated carbon fiber (ACF) can provide a clear understanding of the structural mechanism of steam activation, which would be helpful for designing better micro- and mesoporous carbons. ACFs were reactivated with steam at 973-1173 K. X-ray diffraction and Raman spectroscopy indicated that the stacking number of graphene-like layers of the pore wall decreased with an increase in the reactivation temperature. The average fiber diameter of the ACFs, which was measured via scanning electron microscopy, decreased with the increase in the reactivation temperature. The relationship between the decrease in the fiber diameter and the burn-off suggested that reactivation above 1023 K produced micropores inside the fiber. A deconvolution analysis of the pore-size distribution revealed the variation of the distribution. The peak difference was approximately 0.3 nm, depending on the reactivation temperature. These results indicate that reactivation with steam proceeds via the preferential one-by-one gasification of less-crystalline graphene-like units.

True Picomolar Neurotransmitter Sensor Based on Open-Ended Carbon Nanotubes

Neurotransmitters are important chemicals in human physiological systems for initiating neuronal signaling pathways and in various critical health illnesses. However, concentration of neurotransmitters in the human body is very low (nM or pM level) and it is extremely difficult to detect the fluctuation of their concentrations in patients using existing electrochemical biosensors. In this work, we report the performance of highly densified carbon nanotubes fiber (HD-CNTf) cross-sections called rods (diameter ∼ 69 μm, and length ∼ 40 μm) as an ultrasensitive platform for detection of common neurotransmitters. HD-CNTf rods microelectrodes have open-ended CNTs exposed at the interface with electrolytes and cells and display a low impedance value, i.e., 1050 Ω. Their fabrication starts with dry spun CNT fibers that are encapsulated in an insulating polymer to preserve their structure and alignment. Arrays of HD-CNTf rods microelectrodes were applied to detect neurotransmitters, i.e., dopamine (DA), serotonin (5-HT), epinephrine (Epn), and norepinephrine (Norepn), using square wave voltammetry (SWV) and cyclic voltammetry (CV). They demonstrate good linearity in a broad linear range (1 nM to 100 μM) with an excellent limit of detection, i.e., 32 pM, 31 pM, 64 pM, and 9 pM for DA, 5-HT, Epn, and Norepn, respectively. To demonstrate practical application of HD-CNTf rod arrays, detection of DA in human biological fluids and real time monitoring of DA release from living pheochromocytoma (PC12) cells were performed.

Dealloyed porous gold anchored by in situ generated graphene sheets as high activity catalyst for methanol electro-oxidation reaction

A novel one-step method to prepare the nanocomposites of reduced graphene oxide (RGO)/nanoporous gold (NPG) is realized by chemically dealloying an Al₂Au precursor. The RGO nanosheets anchored on the surface of NPG have a cicada wing like shape and act as both conductive agent and buffer layer to improve the catalytic ability of NPG for methanol electro-oxidation reaction (MOR). This improvement can also be ascribed to the microstructure change of NPG in dealloying with RGO. This work inspires a facile and economic method to prepare the NPG based catalyst for MOR.

A novel one-step method to prepare the nanocomposites of reduced graphene oxide (RGO)/nanoporous gold (NPG) is realized by chemically dealloying an Al₂Au precursor.

Selective capturing of phenolic derivative by a binary metal oxide microcubes for its detection

Development of highly efficient and potential material for toxic p-nitrophenol is an important design for sensitive detection of hazardous species from ecology and environment. Here it is developed, an efficient as well as selective of p-nitrophenol using binary material by electrochemical performances, including good linearity, lower detection limit, good stability, higher reproducibility and extreme sensitivity. The prepared electrode was fabricated by immobilization of SnO₂/CdO microcubes (MCs) with conducting coating binders by using well-known glassy carbon electrode (GCE). The proposed MCs with SnO₂/CdO were well-functionalized and prepared by facile hydrothermal technique. The general instrumentation namely, FTIR, UV/vis, FESEM, XPS, TEM, EDS, and powder XRD were employed for the morphological evaluation of the prepared doped MCs, structural, optical and elemental analyses. The large dynamic range (LDR) from 1.0 to 0.01 mM with 0.13 pM detection limit (S/N = 3), limit of quantification (LOQ; 0.43 pM), and an excellent sensitivity of 7.12 µAµM⁻¹cm⁻² were exhibited by the fabricated binary material based on SnO₂/CdO MCs for selective p-nitrophenol capturing. In shortly, the SnO₂/CdO MCs can be employed as an efficient electron mediator with binary materials fabricated GCE for capturing the p-nitrophenol at ultra-trace amounts. Then the binary synthesized material of SnO₂/CdO MCs is used as potential and sensitive sensor layer by stable electrochemical approach for sensitive capturing of toxic p-nitrophenol from environmental samples.

Aptamer-based thin film gold electrode modified with gold nanoparticles and carboxylated multi-walled carbon nanotubes for detecting oxytetracycline in chicken samples

In this work, a disposable and portable aptasensor for the fast and sensitive detection of oxytetracycline (OTC) using gold nanoparticles (AuNPs)/carboxylated multi-walled carbon nanotubes (cMWCNTs)@thionine connecting complementary strand of aptamer (cDNA) as signal tags was constructed. The substrate electrode of the aptasensor was thin film gold electrode (TFGE), which have the advantages of portable and uniform performance. In the presence of OTC, OTC competed with cDNA to combine with aptamer. The bioconjugate (AuNPs/cMWCNTs/cDNA@thionine) was released from the TFGE. Thus, the electrochemical signal declined. Under optimized conditions, the aptasensor exhibited good stability, high selectivity and high sensitivity. Furthermore, the developed electrochemical aptamer-based TFGE had a wide dynamic range of 1 × 10^-13-1 × 10^-5 g mL^-1 for target OTC with a low detection limit of 3.1 × 10^-14 g mL^-1 and was successfully used for the determination of OTC in chicken sample.

Electrochemiluminescence Quenching Sensor of a Carboxylic Carbon Nanotubes Modified Glassy Carbon Electrode for Detecting Crystal Violet Based on Nitrogen-doped Graphene Quantum Dots@Peroxydisulfate System

In this work, the electrochemiluminscence system of nitrogen-doped graphene quantum dots (N-GQDs) and K₂S₂O₈ was built for the determination of crystal violet (CV). Meanwhile, a carboxylic carbon nanotubes modified glassy carbon electrode (CCNTs/GCE) was used as an ECL sensor. Thanks to the excellent electron transfer ability and large surface area of CCNTs, the ECL signal of N-GQDs@S₂O₈^2- was remarkablely amplified. With the presence of a low concentration of CV, a distinct decrease of the ECL signal was observed due to a quenching effect of CV on the ECL emission. Moreover, the quenched ECL intensity responded linearly to the logarithm of CV concentration within the range of 0.05 - 5 μmol/L, with a LOD of 45 nmol/L (S/N = 3). The proposed ECL system exhibited high sensitivity and specificity to CV, which was successfully applied in the practical detection of CV in real water samples from a local fishpond farm.

High-Throughput 2D Heteroatom Graphene Bioelectronic Nanosculpture: A Combined Experimental and Theoretical Study

In this study, chemical vapor deposition-synthesized heteroatom graphene (HGr) bioelectronic interfaces have been developed for ultrafast, all-electronic detection and analysis of molecules by driving them through tiny holes-or atompores-in a thin lattice of the graphene sheet, including the efforts toward facilitating enhanced electrocatalytic and mapping electron transport activities. The presence of chlorine, nitrogen, and oxygen in the crystalline graphitic layers (<7) has been confirmed using Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. We report a swift bioelectrocatalytic response to step-by-step additions of the substrate with the achievement of a steady current within a few seconds. The response limit was 2.07 μM with a dynamic range of sensing from 2.07 μM to 2.97 mM. The electronic properties and adsorption energies of hydroquinone and p-benzophenone molecule adsorption on pristine, O-, N-, and Cl-doped graphene nanosheet surfaces were systematically investigated using first-principles calculations. The results revealed that the adsorption capacity was improved upon doping graphene nanosheets with O, N, and Cl atoms. Hence, Cl-doped graphene nanosheets were shown as a promising adsorbent toward hydroquinone and p-benzophenone detection.

Highly Uniform, Flexible Microelectrodes Based on the Clean Single-Walled Carbon Nanotube Thin Film with High Electrochemical Activity

Electrochemical sensors based on carbon nanotubes (CNTs) have great potential for use in wearable or implantable biomedical sensor applications because of their excellent mechanical flexibility and biocompatibility. However, the main challenge associated with CNT-based sensors is their uniform and reproducible fabrication on the flexible plastic film. Here, we introduce and demonstrate a highly reliable technique to fabricate flexible CNT microelectrodes on a plastic film. The technique involves a process whereby the CNT film is formed by the dry transfer process based on the floating-catalyst chemical vapor deposition. An oxide protection layer, which is used to cover the CNT thin film during the fabrication process, minimizes contamination of the surface. The fabricated flexible CNT microelectrodes show almost ideal electrochemical characteristics for microelectrodes with the average value of the quartile potentials, Δ E = | E_3/4 - E_1/4|, being 60.4 ± 2.9 mV for the 28 electrodes, while the ideal value of Δ E = 56.4 mV. The CNT microelectrodes also showed enhanced resistance to surface fouling during dopamine oxidation in comparison to carbon fiber and gold microelectrodes; the degradation of the oxidation current after 10 consecutive cycles were 1.8, 8.3, and 13.9% for CNT, carbon fiber, and gold microelectrodes, respectively. The high-sensitivity detection of dopamine is also demonstrated with differential-pulse voltammetry, with a resulting limit of detection of ∼50 nM. The reliability, uniformity, and sensitivity of the present CNT microelectrodes provide a platform for flexible electrochemical sensors.

One-step electrochemically synthesized graphene oxide coated on polypyrrole nanowires as anode for microbial fuel cell

A novel polypyrrole nanowires coated by graphene oxide (PPy-NWs/GO) has been successfully synthesized by one-step electrochemical method, whose structure was different from previously reported PPy/GO composites. The microbial fuel cell equipped with PPy-NWs/GO as anode was fabricated and compared with PPy-NWs ones. The SEM images show that the synthesized PPy-NWs/GO materials possess more surface areas than PPy-NWs. The electrochemical analysis indicated that PPy-NWs/GO anode had lower charge transfer resistance, which may be attributed to synergistic effect of them. The MFC equipped with PPy-NWs/GO anode have higher circle voltages and the power density is about 22.3 mW/m², which is great higher than that of PPy-NWs about 15.9 mW/m². These improvements of the MFCs may be due to more bacteria on the larger biofilms based on GO nanosheets, indicating that the PPy-NWs/GO is more effective anode for improving electricity generation.

An interdigitated electrode with dense carbon nanotube forests on conductive supports for electrochemical biosensors

A highly sensitive interdigitated electrode (IDE) with vertically aligned dense carbon nanotube forests directly grown on conductive supports was demonstrated by combining UV lithography and a low temperature chemical vapor deposition process (470 °C). The cyclic voltammetry (CV) measurements of K4[Fe(CN)6] showed that the redox current of the IDE with CNT forests (CNTF-IDE) reached the steady state much more quickly compared to that of conventional gold IDE (Au-IDE). The performance of the CNTF-IDE largely depended on the geometry of the electrodes (e.g. width and gap). With the optimum three-dimensional electrode structure, the anodic current was amplified by a factor of ∼18 and ∼67 in the CV and the chronoamperometry measurements, respectively. The collection efficiency, defined as the ratio of the cathodic current to the anodic current at steady state, was improved up to 97.3%. The selective detection of dopamine (DA) under the coexistence of l-ascorbic acid with high concentration (100 μM) was achieved with a linear range of 100 nM-100 μM, a sensitivity of 14.3 mA mol-1 L, and a limit of detection (LOD, S/N = 3) of 42 nM. Compared to the conventional carbon electrodes, the CNTF-IDE showed superior anti-fouling property, which is of significant importance for practical applications, with a negligible shift of the half-wave potential (ΔE1/2 < 1.4 mV) for repeated CV measurements of DA at high concentration (100 μM).

Advances in Carbon Nanotubes-Hydrogel Hybrids in Nanomedicine for Therapeutics

In spite of significant advancement in hydrogel technology, low mechanical strength and lack of electrical conductivity have limited their next-level biomedical applications for skeletal muscles, cardiac and neural cells. Host-guest chemistry based hybrid nanocomposites systems have gained attention as they completely overcome these pitfalls and generate bioscaffolds with tunable electrical and mechanical characteristics. In recent years, carbon nanotube (CNT)-based hybrid hydrogels have emerged as innovative candidates with diverse applications in regenerative medicines, tissue engineering, drug delivery devices, implantable devices, biosensing, and biorobotics. This article is an attempt to recapitulate the advancement in synthesis and characterization of hybrid hydrogels and provide deep insights toward their functioning and success as biomedical devices. The improved comparative performance and biocompatibility of CNT-hydrogels hybrids systems developed for targeted biomedical applications are addressed here. Recent updates toward diverse applications and limitations of CNT hybrid hydrogels is the strength of the review. This will provide a holistic approach toward understanding of CNT-based hydrogels and their applications in nanotheranostics.

2-Nitrophenol sensor-based wet-chemically prepared binary doped Co3O4/Al2O3 nanosheets by an electrochemical approach

Herein, the wet-chemical process (co-precipitation) was used to prepare nanosheets (NSs) of Co₃O₄/Al₂O₃ in an alkaline medium (pH ∼ 10.5). The synthesized NSs were totally characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV/vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). The synthesized NSs were deposited onto a glassy carbon electrode (GCE) to prepare a very thin layer with a conducting binder for detecting 2-nitrophenol (2-NP) selectively by a reliable electrochemical method. The proposed chemical sensor exhibits good sensitivity (54.9842 μA μM⁻¹ cm⁻²), long-term stability, and enhanced chemical response by electrochemical approaches. The resultant current is found to be linear over the concentration range (LDR) from 0.01 nM to 0.01 mM. The estimated detection limit (DL) is equal to 1.73 ± 0.02 pM. This study introduces a potential route for future sensitive sensor development with Co₃O₄/Al₂O₃ NSs by an electrochemical approach for the selective detection of hazardous and carcinogenic chemicals in environmental and health care fields.

This potential research work introduces a route of future sensitive sensor development with Co₃O₄/Al₂O₃ NSs by electrochemical approach to selective detection of hazardous and carcinogenic chemicals in environmental and health care fields.