Functionalized Carbon Nanotubes Research Articles

Superior energy storage and stability realized in flexible carbon nanotube aerogel-metal organic framework based supercapacitor via interface engineering

Our present study unveils a new carbon nanotube aerogel-metal organic framework free-standing electrode, showcasing exceptional dual functionality as an electrode and current collector. In the prepared electrode, an interface engineering between functionalized carbon nanotubes (FCNT) and metal-organic frameworks (MOF) leads to the excellent electrochemical performance of the supercapacitor. The carbon nanotube aerogel with its exceptional surface area and electrical conductivity, lays the foundation for lightning-fast charge transfer. Meanwhile, the metal-organic frameworks present at the interface, grant ions unbridled storage space contributing to efficient charge storage. The ulta-light-in-weight FCNT-MOF free-standing electrode exhibited an excellent specific capacitance of 465 F g−1 (116 mF cm−2) at 2 A g−1 with outstanding cyclic stability of 92 % after 6000 cycles. The flexible FCNT-MOF symmetric supercapacitor demonstrated a high energy density of 40.5 W h kg−1 at a power density of 1600 W kg−1. The simplified fabrication process, reduced active material requirements (0.25 mg cm−2), and enhanced performance make it an attractive option for supercapacitor application. Furthermore, the integration of this electrode design into supercapacitors holds great promise for portable electronics, electric vehicles, and renewable energy systems.

Evaluation of synthesized MWCNTs-COO@Fe3O4 nanocomposite based on laser-assisted method for highly-efficient clean water

In this study, the surface of MWCNTs was treated with acid by adding a carboxyl group to be ready to load nanostructured materials on their surface in a novel way. The femtosecond laser ablation process was used for decorating magnetic nanoparticles (Fe3O4) on the functionalized carbon nanotubes (MWCNTs-COOH) to form the MWCNTs-COO@Fe3O4 nanocomposite structure to be used for the heavy metal removal of Pb(II). Different techniques have all been used to identify the functionality groups that are present on the MWCNTs. Raman spectroscopy showed the decrease of G band when Fe3O4 nanoparticles embedded MWCNTs-COOH, indicating a greater degree of defect in MWCNTs. VSM showed the magnetic characteristic properties of the composite. XRD showed the reduction of MWCNTs diffraction peaks after embedding with iron oxide, explained the partial full coverage of the MWCNTs surface by the Fe3O4 nanoparticles. FT-IR showed the composite exhibit a peak at 579 cm−1, which is brought on by the Fe–O stretching vibrational modes. Zeta potential showed the surface of the MWCNTs-COO@Fe3O4 had a more positive charge under neutral pH compared with that of MWCNTs. TGA showed the weight loss of MWCNTs-COO@Fe3O4 was greater than that of MWCNTs, confirming the interaction of some Fe3O4 on MWCNTs-COOH. Also, tested pH, contact time, initial Pb (II) concentration, and adsorbent mass were carried to improve Pb (II) ion adsorption on the nanocomposite. The optimal removal effectiveness of Pb (II) on the MWCNTs-COO@Fe3O4 nanocomposite is attained when the experiment is conducted at a pH of 6, with a contact time of 10 min, an initial concentration of 100 mg/L, and under alkaline conditions. Pb (II) ions were adsorbing using a pseudo-second-order equation to reflect their chemical adsorption, with a rate constant of (k2 = 0.00446 g mg−1 min−1). The highest adsorption capacity obtained was 66.85 mg g−1. MWCNTs-COO@Fe3O4 nanocomposite efficiently collected Pb (II) utilizing green and easy to use method to protect public health.

Removal of organochlorine pesticides by nanofiltration membranes modified with NH2-MWCNTs

Excessive use of pesticides and therefore the spread of pesticides in the environment with destructive effects on human and animal health is a very great problem in the world. In this study, the removal of three samples of organochlorine pesticides including aldrin, lindane, and endosulfan was investigated using nanofiltration membranes modified with NH2-MWCNTs. The properties of the prepared membranes were investigated by scanning electron microscopy (SEM), contact angle, water content, porosity, and mechanical strength. The performance of the membranes was evaluated by analysis of the rejection and flux of pesticide solutions at different pH. The addition of NH2-MWCNTs to the polymer matrix significantly improved the hydrophilic properties of the membranes and reduced the contact angle. Membrane flux was also improved by increasing the concentration of carbon nanotubes to 0.2 wt%. The highest flux at pH 10 is related to lindane pesticide. The modified membrane with 0.5 wt% functionalized carbon nanotubes showed a 98% rejection for endosulfan at neutral pH compared to the pure membrane. In the pH range experiment, lindane rejection was lower than of other pesticides. The steric hindrance due to the structure and molecular size of pesticides and interaction with membrane surface was very important in membrane efficiency. The M3 membrane with 0.3 wt% NH2-MWCNTs revealed high antifouling performance.

Effects of polyurethane/functionalised carbon nanotube interfacial interactions on tensile and compressive properties – molecular dynamics simulations

In order to understand the enhancement mechanism of the interaction between functionalised carbon nanotubes and polymer matrix, and to investigate the effects of different functionalised carbon nanotubes on the properties of composites at the microscopic level, the models of pure polyurethane (PUR), carbon nanotubes/polyurethane (CNTs/PUR), hydroxyl-functionalised carbon nanotubes/polyurethane (CNTOH/PUR), and carboxyl-functionalised carbon nanotubes/polyurethane (CNTCOOH/PUR) systems were constructed, and molecular dynamics methods were used to simulate the effects of different functionalised carbon nanotubes on the mechanical properties of polyurethane composite systems. The effects of different functionalised carbon nanotubes on the properties of PUR composite systems were compared by analysing the properties of PUR and its composite systems in terms of free volume fraction (FFV), radial distribution function (RDF), binding energy, and density distribution of PUR around different functionalised carbon nanotubes. The effects of intermolecular interactions on the properties of the composite systems were elucidated at the microscopic level. The final simulation results show that the CNTCOOH/PUR composite system with added carboxylated CNTs has the highest tensile yield strength, compressive properties and modulus; the smallest free volume fraction; the strongest bonding energy between CNTCOOH and PUR matrix, the largest density distribution of PUR matrix around CNTCOOH, and the best interfacial interaction.

Modeling the Interaction between the Isoniazid Anti-Tuberculosis Drug and Functionalized Carbon Nanotubes for Medical Applications: A Quantum Chemical Study

Introduction: The purpose of using nano-carriers for drugs delivery, such as nanotubes, was slow release of drug and reducing side effects of drugs. Drugs are very active due to their many functional groups. Therefore, reactivity of drug is reduced by being in nanotube field due to electronic resonance of drug with nanotube and it stays longer in body. The present study aimed to investigate the interaction of isoniazid with functionalized single-walled carbon nanotubes.
 Methods: In the present theoretical study, considering the importance of isoniazid as the first line of treatment for tuberculosis disease, the performance of carbon nanostructures for adsorption of isoniazid was evaluated using quantum computation. Using density functional theory at theoretical level of B3LYP/6-31G** structure of drug and f-SWCNT and nano-drug complexes were optimized.
 Results: Effect of adsorption on the electronic properties and stability of the nanotube was also examined. In this regard, for different configurations, the strength and nature of intermolecular interactions were evaluated by energy parameters and molecular orbitals. Based on the obtained results, a specific configuration displayed the most negative adsorption energy and enthalpy, establishing itself as the most stable structure among the various configurations.
 Conclusion: Results showed that the electron density of the HOMO (Highest Occupied Molecular Orbital) was localized on the nanotube, while the electron density of the LUMO (Lowest Unoccupied Molecular Orbital) was situated on the drug molecule. The energy gap between two molecular orbitals increased due to the adsorption process; changes lead to an increase in the electrical conductivity of the complex following adsorption. According to the natural bond orbitals, results, the isoniazid molecule and functionalized single-walled carbon nanotube act as both electron donor and acceptor in the complex. Analysis of the results obtained from quantum theory of atoms in molecules, showed the intermolecular interaction between the drug and the functional group of the nanotube has been established, the most important of which is the hydrogen bond. Finally, the findings showed that functionalized SWCNTs can be acted as a drug carrier for isoniazid anti-tuberculosis drug.

Superhydrophobic composite membranes for membrane distillation based on CNTs networks: Overcoming the trade-off between water vapor permeability and wetting resistance

Enhancing the wetting resistance of the membrane is crucial for consolidating the stability of the membrane distillation (MD) process, but this generally leads to the decline of water vapor flux. Herein, we developed a superhydrophobic composite membrane composed of a highly hydrophobic polyvinylidene fluoride (PVDF) porous support layer and a functional superhydrophobic carbon nanotubes (CNTs) network. The CNTs network with high thermal conductivity not only reduces the temperature polarization effect, but also increases the effective evaporation area, thereby enhancing the mass transfer driving force of the MD process. Additionally, the CNTs network significantly reduces the maximum pore radius of the composite membrane, and the perfluorination treatment also reduces the surface energy of the CNTs network, thereby synergistically increasing the liquid entry pressure. The results showed that when treating high salinity water containing 3.5 wt% NaCl, the water vapor flux of the composite membrane increased from 20.0 LMH of the original PVDF membrane to 24.4 LMH, an increase of 22 %. Furthermore, the performance of the original PVDF membrane deteriorates rapidly when the concentration of surfactant in the feed exceeds 1.0 mM, while the composite membrane still maintains a stable water vapor permeability and salt rejection. More importantly, the composite membrane exhibits excellent resistance to wetting induced by gypsum scaling when using gypsum solution as the feed, which is attributed to its small surface pore size and high hydrophobicity. This research supplies new insights into the design of membrane structures used in MD processes to overcome the trade-off between water vapor permeability and wetting resistance.

Seamless Integration of Rapid Separation and Ultrasensitive Detection for Complex Biological Samples Using Multistage Annular Functionalized Carbon Nanotube Arrays.

Efficient separation, enrichment, and detection of bacteria in diverse media are pivotal for identifying bacterial diseases and their transmission pathways. However, conventional bacterial detection methods that split the separation and detection steps are plagued by prolonged processing times. Herein, a multistage annular functionalized carbon nanotube array device designed for the seamless integration of complex biological sample separation and multimarker detection is introduced. This device resorts to the supersmooth fluidity of the liquid sample in the carbon nanotubes interstice through rotation assistance, achieving the ability to quickly separate impurities and capture biomarkers (1mL sample cost time of 2.5 s). Fluid dynamics simulations show that the reduction of near-surface hydrodynamic resistance drives the capture of bacteria and related biomarkers on the functionalized surface of carbon nanotube in sufficient time. When further assembled as an even detection device, it exhibited fast detection (<30min), robust linear correlation (101-107 colony-forming units [CFU] mL-1, R2 = 0.997), ultrasensitivity (limit of detection = 1.7 CFU mL-1), and multitarget detection (Staphylococcus aureus, extracellular vesicles, and enterotoxin proteins). Collectively, the material and system offer an expanded platform for real-time diagnostics, enabling integrated rapid separation and detection of various disease biomarkers.

Optimization of Magnetic Dielectric Nanocomposites Obtained by Facile and Low-Cost Fabrication for Effective Absorption of Electromagnetic Waves

This work presents the synthesis of Fe3 O4 nanoparticles (FNPs) and nanocomposites (NCs) of FNPs and functionalized carbon nanotubes (CNTs) at varying weight ratios for application in 8–18 GHz electromagnetic waves (EMW) absorbers. Their dielectric, magnetic, and structural characteristics were also examined. To create the desired NCs, CNTs are first mixed with FNPs at various weight ratios. The magnetic properties of the samples were ascertained using a vibrating sample magnetometer, and the dielectric properties of all the samples were examined by a vector network analyzer at room temperature after the crystal structure of the samples was determined by X-ray diffraction, surface morphology, and elemental analysis by scanning electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. Fe3 O4 @CNTs NCs in six different weight ratios (NC1 -NC6 ) were prepared. Sample NC3 , with a thickness of 2.25 mm, exhibited the greatest loss in the X band, measuring -27.07 dB, out of all the samples. Additionally, the NC4 sample which has a thickness of 5.00 mm, had the best loss, which came in at -38.21 dB in the Ku band. A data-driven method developed for multi-parameter optimization was then used to find out the optimal ratio weight ratio and sample thickness based on the experimental data. Samples with minimum reflection loss -34.1 dB (-41.5 dB), and others with effective bandwidth coving 69.0 % (71.4 %) in the X band (Ku band) were obtained.

Ionic liquid in-situ functionalized carbon nanotube film as self-supported metal-free electrocatalysts for oxygen evolution

The oxygen evolution reaction (OER) is a critical cathode reaction for hydrogen production from water splitting. However, due to the sluggish kinetics of OER, the water-splitting process is impeded. Thus, it is imperative to develop efficient and low-cost electrocatalysts that reduce the overpotential and improve the kinetics of OER. Herein, an in-situ synthesis strategy was applied to prepare the ionic liquid functionalized carbon nanotube (IL-CNT) that served as a metal-free electrocatalyst for OER. This powder material exhibited exceptional electrocatalytic activity for OER, with an overpotential of 335 mV at 10 mA cm−2 and a Tafel slope of 71 mV dec-1. Then, it was found that catalytic activity was influenced by the IL anion. Moreover, this IL-CNT powder could self-assemble to form carbon film during preparation, exhibiting outstanding catalytic activity for OER (a low overpotential of 153 mV at 10 mA cm−2), which was highly beneficial for practical application. Based on the theoretical calculations and experimental results, these in-situ functionalization sites on CNT surface played a significant role in regulating their electron structure. This, in turn, promoted electron transfer and hydroxyl adsorption, resulting in a substantial increase in catalytic activity for the OER.

Heteroatom‐Doped Carbon Nanotube Membranes from Waste Biomass for Photoelectro‐Catalytic Water Purification

AbstractPrinting and dyeing wastewater, that is discharged after textile printing and dyeing processing, can cause irreversible damage to the aquatic ecosystem and harm the health of human beings. Till now, completely and readily removing dye molecules from industrial wastewater using a single catalyst rather than the combination of several materials remains a significant challenge. Herein, in situ preparation of carbon nanotube membranes (N‐CNTM and N‐TiO2‐CNTM) are reported that are doped using N with/without TiO2, respectively. These membranes can simultaneously function as an adsorber, a photo‐catalyst, and an electrocatalyst to efficiently remove dye pollutes from industrial waste water. Further researches reveal that the formation of p‐n type heterojunction inside of the N‐CNTM and N‐TiO2‐CNTM, can improve the hole separation and charge storage abilities, resulting in the efficient removal of dyes in the industrial waste water. This work provides a promising approach for the preparation of functionalized carbon nanotubes derived from waste biomass for the treatment of industrial water, reflecting the concept of treating waste with waste.

A molecular dynamics study for the extraction of cesium from aqueous solutions in the presence of functionalized carbon nanotube

ABSTRACT Molecular dynamics (MD) simulation was conducted to obtain the interfacial behavior of cesium (Cs+) extraction by functionalized carbon nanotubes (CNTs). The present study explores the extraction mechanism of Cs+ with functional groups such as OCH(CH3)2, and CONH2-based CNTs. The results display that adsorption capacity is improved significantly using a surface modification of a single-walled carbon nanotube (SWCNT) with isopropoxide and amide functional groups. The studies investigate the separation of Cs+ in the presence of functionalized CNTs from the ionic liquid (IL) – water biphasic systems. It has been found that CNT with OCH(CH3)2 functional group is highly efficient for Cs+ extraction as compared to the CONH2 group and bare CNT. The higher interaction energy between Cs+ and CNT with OCH(CH3)2 functional group (˗84.41 kcal/mol) was observed at the interface when compared with bare CNT (˗4.34 kcal/mol). In general, the order of Cs+ ion adsorption capacity on the CNT surface is CNT – OCH(CH3)2 > CNT – CONH2 > bare CNT. The current study offers quantitative data and insights into the extraction of metal ions with functionalized CNTs, which may be highly helpful for future technological exploration of the many nano-adsorbent-based investigations.

Exploring the Role of Carbon Nanotubes in Mitigating the Effects of Climate Change: A Comprehensive Review

‌This article provides the role of carbon nanotubes (CNTs) in mitigating the effects of climate change. CNTs possess unique properties that make them attractive for various applications aimed at addressing climate-related challenges. This review examines the potential contributions of CNTs in key areas, including energy storage, carbon capture and storage (CCS). In the field of energy storage, CNT-based materials demonstrate high-energy density and fast charge-discharge rates, enabling more efficient energy storage and facilitating the integration of renewable energy sources. This advancement offers promising opportunities for reducing reliance on fossil fuels and promoting a sustainable energy landscape. Regarding CCS, CNTs exhibit exceptional adsorption capabilities, making them effective adsorbents for capturing carbon dioxide (CO2) emissions from industrial sources. Additionally, CNTs can serve as catalyst supports for CO2 conversion, enabling the conversion of CO2 into valuable products and contributing to greenhouse gas reduction efforts. In conclusion, carbon nanotubes hold substantial promise in mitigating climate change. Future research and development efforts should focus on optimizing CNT synthesis techniques, functionalization methods, and characterization approaches to fully harness their potential. By advancing the applications of CNTs, we can contribute to a sustainable and low-carbon future.

Synthesis, characterization and optimization of sulfonated poly-ether-ether-ketone (sPEEK)/functionalized carbon nanotubes (c-CNTs) nanocomposite membranes for fuel cell application

Poly-ether ketone (PEEK) was modified to sulfonated poly-ether ketone (sPEEK) by sulfonation process with a degree of sulfonation 49.5%. Carbon nanotubes were acid-treated with sulfuric acid and nitric acid solution (3:1, v/v) for functionalization. sPEEK and sPEEK/c-CNT membranes were prepared by solvent casting method using dimethyl sulfoxide (DMSO) as solvent. The experimental part was conducted as per design of experiment employing response surface methodology consisting of three factors, namely (A) c-CNT (wt.%), (B) mixing temperature (°C), and (C) sPEEK concentration (mg/mL). The ion exchange capacity was found to increase with c-CNT (wt.%). Fourier-transform infrared spectroscopy confirms the sulfonation of PEEK. X-Ray diffraction investigates the influence of the sulfonation in the crystal structure of the sPEEK and sPEEK/c-CNT. Scanning electron microscopy images show that c-CNTs are dispersed well in the sPEEK matrix. The results showed slightly increasing water uptake and swelling ratio of the composites membranes. The analysis of variance (ANOVA) revealed that c-CNT (wt.%) is highly affecting the responses. Proton conductivity of sPEEK specimen is about 23.9 mS/cm, which is significantly increased to 57.0 mS/cm for sPEEK/0.12 c-CNT (wt.%) membrane suggesting its application for fuel cell.

Heat transfer and energy performance analysis of photovoltaic thermal system using functionalized carbon nanotubes enhanced phase change material

The photovoltaic thermal system (PVT) is an emerging technology that simultaneously generates both electrical and thermal energy from solar energy, aiming to improve solar energy utilization. However, significant technological issues with these systems obstruct their large-scale operation. The major drawback of the cooling fluid-based PVT systems lies in operation during sun-shine hours only. To address this issue, the present research endeavors a comparative study on with and without nano-enhanced phase change materials (NePCM) integrated PVT system. In this study, the performance evaluation of four configurations was analyzed with a flow rate varying from 0.4 to 0.8 litter per minute. From this, the experimental analysis was performed on two systems, including a photovoltaic and a PVT system. The simulation was performed using TRNSYS simulation on the phase change materials integrated photovoltaic thermal system, and NePCM integrated photovoltaic thermal system. The results indicates that increasing the flow rate by 2.2 times leads to a 4.9-fold increase in pressure drop, while the friction factor decreases with rising mass flow rate. Notably, the NePCM-integrated PVT system exhibited a substantial reduction in cell temperature and increased electrical power output at higher flow rates. At a flow rate of 0.4litter per minute, a significant heat gain was achieved with an impressive energy-saving efficiency of 75.67 %. Furthermore, the total efficiency of the PVT system, phase change materials integrated PVT system, and NePCM integrated PVT system were determined to be 81.9 %, 84.5 %, and 85.05 %, respectively. These findings underscore the potential of NePCM-integrated PVT systems for enhancing performance and expanding their practical application.

Molecular dynamics study of the mechanical properties of hydrated calcium silicate enhanced by functionalized carbon nanotubes.

The incorporation of functionalized carbon nanotubes can enhance the mechanical properties of cement-based materials. However, the types of functional groups and their roles in composite materials are not yet clear. In this study, molecular dynamics (MD) simulation methods were employed to investigate the mechanical performance of hybridized calcium silicate hydrate gel reinforced with pure carbon nanotubes, epoxy-coated carbon nanotubes, carboxylated carbon nanotubes, and hydroxylated carbon nanotubes. The results indicate that the addition of all four types of nanotubes can enhance the mechanical properties of hydrated calcium silicate gel compared to pure C-S-H. Tensile loading results show that carbon nanotubes can act as bridges for microcracks in the composite material, and functionalized nanotubes exhibit a better reinforcing effect than pure carbon nanotubes. Under tensile stress, hydroxylated nanotubes are more effective in increasing the toughness of the composite material, while carboxylated nanotubes tend to enhance the strength of the composite material. The compressive loading results indicate that the compressive strength of cement-based materials is higher than their tensile strength. Overall, carboxylated nanotubes show particularly remarkable performance in enhancing the mechanical properties of cement-based materials. Compared to pure C-S-H gel, the tensile and compressive elastic moduli of carboxylated nanotube/C-S-H composite material increased by 18.13% and 34.78%, respectively. Its tensile and compressive strengths also increased by 30.40% and 40.23%, respectively. All molecular dynamics simulations were performed on the classical computational simulation platform LAMMPS. In this paper, the parameters in the ClayFF force field are chosen to simulate calcium hydrated silicate (/C-S-H), and the ClayFF-CVFF combined force field is used to simulate the mechanical properties of the CNT/C-S-H molecular model structure.

Synthesis of Bimetallic Nickel-Cobalt Nanoparticles Supported by Functional Multi-Walled Carbon Nanotubes by Chemical Methods: Characterization and Hydrogen Energy Generation

Synthesis of Bimetallic Nickel-Cobalt Nanoparticles Supported by Functional Multi-Walled Carbon Nanotubes by Chemical Methods: Characterization and Hydrogen Energy Generation

Functionalized Carbon Nanotubes for Delivery of Ferulic Acid and Diosgenin Anticancer Natural Agents.

It was investigated whether loading multi-wall carbon nanotubes (CNTs) with two natural anticancer agents: ferulic acid (FUA) and diosgenin (DGN), may enhance the anticancer effect of these drugs. The CNTs were functionalized with carboxylic acid (CNTCOOH) or amine (CNTNH2), loaded with the above pro-drugs, as well as both combined and coated with chitosan or chitosan-stearic acid. Following physicochemical characterization, the drug-loading properties and kinetics of the drug's release were investigated. Their effects on normal human skin fibroblasts and MCF-7 breast carcinoma cells, HepG2 hepatocellular carcinoma cells, and A549 non-small-cell lung cancer cells were evaluated in vitro. Their actions at the molecular level were evaluated by assessing the expression of lncRNAs (HULC, HOTAIR, CCAT-2, H19, and HOTTIP), microRNAs (mir-21, mir-92, mir-145, and mir-181a), and proteins (TGF-β and E-cadherin) in HepG2 cells. The release of both pro-drugs depended on the glutathione concentration, coating, and functionalization. Release occurred in two stages: a no-burst/zero-order release followed by a sustained release best fitted to Korsmeyer-Peppas kinetics. The combined nanoformulation cancer inhibition effect on HepG2 cancer cells was more pronounced than for A549 and MCF7 cells. The combined nanoformulations had an additive impact followed by a synergistic effect, with antagonism demonstrated at high concentrations. The nanoformulation coated with chitosan and stearic acid was particularly successful in targeting HepG2 cells and inducing apoptosis. The CNT functionalized with carboxylic acid (CNTCOOH), loaded with both FUA and DGN, and coated with chitosan-stearic acid inhibited the expression of lncRNAs and modulated both microRNAs and proteins. Thus, nanoformulations composed of functionalized CNTs dual-loaded with FUA and DGN and coated with chitosan-stearic acid are a promising drug delivery system that enhances the activity of natural pro-drugs.

Effective Cu-Fe oxide/ multidimensional nanocarbon-coupled ternary composite-based anode: Mechanistic insight into interface tuning for swift Li-ion diffusion

This work focused on engineering the hybrid nanocomposite-based anode comprising CuFe2O4 (CFO), reduced graphene oxide (RG), and functionalized carbon nanotubes (FC) to investigate its Li-ion storage kinetics. The ternary nanocomposites CFO/RG/FC (CFO-C) demonstrated a specific capacity (SC) of 760 mAh/g at a Cdensity of 200 mA/g after 100 electrochemical charge-discharge cycles and an SC of 450 mAh/g at a high Cdensity of 500 mA/g after 300 electrochemical cycles. Results revealed that the addition of RG and FC aided in enhancing the electrical transport at the interface, in turn, it assisted in augmenting the Li-ion storage capability from ∼240 to ∼760 mAh/g at the end of 100 charge-discharge cycles with a Cdensity of 200 mA/g. RG and FC acted as anchoring sites for CFO and spacer, respectively, which resulted in improved electrical transport to accelerate Li-ion diffusion transport by fivefold. Such composite anode is a probable candidate as the high-performance anode in designing high-energy density Li-ion battery applications.

Kirigami-inspired gas sensors for strain-insensitive operation

Wearable electronics for the Internet of Things (IoT) have spurred interest in optimizing stretchable substrates, electrodes, and sensing materials. Specifically, wearable gas sensors are valuable for real-time monitoring of hazardous chemicals. For wearable gas sensors, a stable operation under mechanical deformation is required. Here, we introduce strain-insensitive Kirigami-structured gas sensors decorated with titanium dioxide (TiO2) functionalized carbon nanotubes (CNTs) for NO2 sensing. The Kirigami-shaped substrate is used to ensure mechanical stability when stretched. The developed device shows only a 1.3 % change in base resistance under 80 % strain. In addition, the impact of electro-thermal properties at various strain levels is analyzed to aid the understanding of the device's performance. The CNT-TiO2 composite induced alterations in p-n heterojunctions, improving the measurement sensitivity by approximately 250 % compared to a bare CNT sensor. Additionally, the sensors exhibited a 10-fold faster desorption rate due to the enhanced photocatalytic effect of TiO2 under UV exposure. Remarkably, the Kirigami-structured gas sensors maintained stable and repetitive sensing operation even under 80 % strain, which would be enough to be used in various wearable applications.

Polymeric integration of structure-switching aptamers on transistors for histamine sensing.

Aptamers that undergo large conformational rearrangements at the surface of electrolyte-gated field-effect transistor (EG-FETs)-based biosensors can overcome the Debye length limitation in physiological high ionic strength environments. For the sensitive detection of small molecules, carbon nanotubes (CNTs) that approach the dimensions of analytes of interest are promising channel materials for EG-FETs. However, functionalization of CNTs with bioreceptors using frequently reported surface modification strategies (e.g., π-π stacking), requires highly pristine CNTs deposited through methods that are incompatible with low-cost fabrication methods and flexible substrates. In this work, we explore alternative non-covalent surface chemistry to functionalize CNTs with aptamers. We harnessed the adhesive properties of poly-D-lysine (PDL), to coat the surface of CNTs and then grafted histamine-specific DNA aptamers electrostatically in close proximity to the CNT semiconducting channel. The layer-by-layer assembly was monitored by complementary techniques such as X-ray photoelectron spectroscopy, optical waveguide lightmode spectroscopy, and fluorescence microscopy. Surface characterization confirmed histamine aptamer integration into PDL-coated CNTs and revealed ∼5-fold higher aptamer surface coverage when using CNT networks with high surface areas. Specific aptamers assembled on EG-CNTFETs enabled histamine detection in undiluted high ionic strength solutions in the concentration range of 10 nM to 100 μM. Sequence specificity was demonstrated via parallel measurements with control EG-CNTFETs functionalized with scrambled DNA. Histamine aptamer-modified EG-CNTFETs showed high selectivity vs. histidine, the closest structural analog and precursor to histamine. Taken together, these results implied that target-specific aptamer conformational changes on CNTs facilitate signal transduction, which was corroborated by circular dichroism spectroscopy. Our work suggests that layer-by-layer polymer chemistry enables integration of structure-switching aptamers into flexible EG-CNTFETs for small-molecule biosensing.