High-Power-Density and Excellent-Flexibility Thermoelectric Generator Based on All-SWCNTs/PVP Composites.

Flexible polymer/single-wall carbon nanotube (SWCNT) composites are a vital component for wearable/portable electronics, but the development of their n-type counterpart is laggard. Furthermore, little attention is paid to the interaction between SWCNT and polymers, especially the unconjugated polymers, as well as the conversion mechanism of conduction characteristics. Here, the n-type flexible SWCNTs/Polyvinyl Pyrrolidone (PVP) films are successfully fabricated, where the oxygen atoms in PVP interacted with SWCNT via hydrogen bonds, which can lower the energy barrier of electron tunneling, providing the pathway for the electron transfer. Furthermore, with the increasing synthesis temperature, the hydrogen bonds strengthened and the thermal activation energy further improved, both of which enhanced the electron-donating ability of PVP, resulting in a high-power-factor value of 260 µW m-1 K-2. Based on the optimized SWCNTs/PVP films, a thermoelectric module is assembled, which achieved a power density of 400 µW cm-2 at a temperature difference of 56 K, coupled with excellent flexibility, showing a less than 1% variation of resistance after 5000 bending cycles. It shows the highest output-performance and the best flexibility among the reported SWCNT-based thermoelectric modules. This work provides significant insights into the interaction mechanism and performance optimization of hybrid thermoelectric composites, based on SWCNTs/unconjugated polymers.

An Automated Gradient Titration Fluorescence Methodology for High-Resolution Identification of Aqueous Two-Polymer Phase Extraction Conditions for Single-Wall Carbon Nanotubes.

A significant advance in rate and precision of identifying the co-surfactant concentrations leading to differential extraction of specific single-wall carbon nanotube (SWCNT) species in aqueous two-polymer phase extraction experiments is reported. These gains are achieved through continuous titration of co-surfactant and other solution components during automated fluorescence measurements on SWCNT dispersions. The resulting fluorescence versus concentration curves display intensity and wavelength shift transitions traceable to the nature of the adsorbed surfactant layer on specific SWCNT structures at the (n,m) species and enantiomer level at high resolution. The increased precision and speed of the titration method resolve previously invisible complexity in the SWCNT fluorescence during the transition from one surfactant dominating the SWCNT interface to the other, offering insight into the fine details of the competitive exchange process. For the first time, we additionally demonstrate that the competitive process of the surfactant switch is direction independent (reversible) and hysteresis-free; the latter data effectively specifies an upper bound for the time scale of the exchange process. Titration curves are compared to literature results and initial advanced parameter variation is conducted for previously unreasonable to investigate solution conditions.

Highly Sensitive Pressure Sensor Based on Elastic Conductive Microspheres.

Elastic pressure sensors play a crucial role in the digital economy, such as in health care systems and human-machine interfacing. However, the low sensitivity of these sensors restricts their further development and wider application prospects. This issue can be resolved by introducing microstructures in flexible pressure-sensitive materials as a common method to improve their sensitivity. However, complex processes limit such strategies. Herein, a cost-effective and simple process was developed for manufacturing surface microstructures of flexible pressure-sensitive films. The strategy involved the combination of MXene-single-walled carbon nanotubes (SWCNT) with mass-produced Polydimethylsiloxane (PDMS) microspheres to form advanced microstructures. Next, the conductive silica gel films with pitted microstructures were obtained through a 3D-printed mold as flexible electrodes, and assembled into flexible resistive pressure sensors. The sensor exhibited a sensitivity reaching 2.6 kPa-1 with a short response time of 56 ms and a detection limit of 5.1 Pa. The sensor also displayed good cyclic stability and time stability, offering promising features for human health monitoring applications.

Polydopamine/SWCNT Ink Functionalization of Silk Fabric to Obtain Electroconductivity at a Low Percolation Threshold.

This study presents the functionalization of silk fabric with SWCNT ink. The first step was the formation of a polydopamine (PDA) thin coating on the silk fabric to allow for effective bonding of SWCNTs. PDA formation was carried out directly on the fabric by means of polymerization of dopamine in alkali conditions. The Silk/PDA fabric was functionalized with SWCNT ink of different SWCNT concentrations by using the dip-coating method. IR and Raman analyses show that the dominant ß-sheet structure of silk fibroin after the functionalization process remains unchanged. The heat resistance is even slightly improved. The hydrophobic silk fabric becomes hydrophilic after functionalization due to the influence of PDA and the surfactant in SWCNT ink. The ink significantly changes the electrical properties of the silk fabric, from insulating to conductive. The volume resistance changes by nine orders of magnitude, from 2.4 × 1012 Ω to 2.3 × 103 Ω for 0.12 wt.% of SWCNTs. The surface resistance changes by seven orders of magnitude, from 2.1 × 1012 Ω to 2.4 × 105 Ω for 0.17 wt.% of SWCNTs. The volume and surface resistance thresholds are determined to be about 0.05 wt.% and 0.06 wt.%, respectively. The low value of the percolation threshold indicates efficient functionalization, with high-quality ink facilitating the formation of percolation paths through SWCNTs and the influence of the PDA linker.

Simultaneous Inside and Outside Functionalization of Single-Walled Carbon Nanotubes.

Functionalizing single-walled carbon nanotubes (SWCNTs) in a robust way that does not affect the sp2 carbon framework is a considerable research challenge. Here we describe how triiodide salts of positively charged macrocycles can be used not only to functionalize SWCNTs from the outside, but simultaneously from the inside. We employed disulfide exchange in aqueous solvent to maximize the solvophobic effect and therefore achieve a high degree of macrocycle immobilization. Characterization by Raman spectroscopy, EDX-STEM and HR-TEM clearly showed that serendipitously this wet-chemical functionalization procedure also led to the encapsulation of polyiodide chains inside the nanotubes. The resulting three-shell composite materials are redox-active and experience an intriguing interplay of electrostatic, solvophobic and mechanical effects that could be of interest for applications in energy storage.

Introduction of an electrochemical point-of-care assay for quantitative determination of paracetamol in finger-prick capillary whole blood samples.

AIMS: Measuring venous plasma paracetamol concentrations is time- and resource-consuming. We aimed to validate a novel electrochemical point-of-care (POC) assay for rapid paracetamol concentration determinations. METHODS: Twelve healthy volunteers received 1 g oral paracetamol, and its concentrations were analysed 10 times over 12 h for capillary whole blood (POC), venous plasma (high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS)), and dried capillary blood (HPLC-MS/MS). RESULTS: At concentrations >30 µM, POC showed upward biases of 20% (95% limits of agreement [LOA] -22 to 62) and 7% (95% LOA -23 to 38) compared with venous plasma and capillary blood HPLC-MS/MS, respectively. There were no significant differences between mean concentrations for the paracetamol elimination phase. CONCLUSIONS: Upward biases in POC compared with venous plasma HPLC-MS/MS were likely due to higher paracetamol concentrations in capillary blood than in venous plasma and to faulty individual sensors. The novel POC method is a promising tool for paracetamol concentration analysis.

Improving the linearity of synaptic plasticity of single-walled carbon nanotube field-effect transistors via CdSe quantum dots decoration.

The linearity of synaptic plasticity of single-walled carbon nanotube field-effect transistor (SWCNT FET) was improved by CdSe quantum dots decoration. The linearity of synaptic plasticity in SWCNT FET with decorating QDs was further improved by reducing the P-type doping level from the atmosphere. The synaptic behavior of SWCNT FET is found to be dominated by the charging and discharging processes of interface traps and surface traps, which are predominantly composed of H2O/O2redox couples. The improved synaptic behavior is mainly due to the reduction of the interface trap charging process after QDs decoration. The inherent correlation between the device synaptic behavior and the electron capture process of the traps are investigated through charging-based trap characterization. This study provides an effective scheme for improving linearity and designing new-type SWCNT synaptic devices.

Compositional Analysis of ssDNA-Coated Single-Wall Carbon Nanotubes through UV Absorption Spectroscopy.

Aqueous suspensions of single-wall carbon nanotubes (SWCNTs) coated by ssDNA are analyzed using UV absorption and total carbon measurements. The results give absolute average concentrations of both components in samples without free ssDNA. From those values, the average mid-UV SWCNT absorptivity is deduced for three different batches of relatively small diameter nanotubes: two HiPco and one CoMoCAT. The absorptivity values enable the use of simple spectrophotometry to measure absolute concentrations of similar SWCNT samples in aqueous SDS. The results also quantify the mass ratio of ssDNA to SWCNT, defining the average number of nanotube carbon atoms suspended by one ssDNA strand of T15GT15 or T30G. Comparing this experimental parameter with results from replica exchange molecular dynamics simulations of one ssDNA strand freely adsorbed on a (6,5) segment shows close agreement between the computed number of SWCNT atoms covered per strand and the measured number of SWCNT atoms suspended per strand.

Graphene and graphene nanohybrid composites-based electrodes for physiological sensing applications.

In this paper, three categories of ECG electrodes were fabricated. Graphene/PDMS(Polydimethylsiloxane)(G-I), Graphene/MWCNT-COOH(Carboxylic-acid functionalized Multi-walled Carbon Nanotubes)/PDMS(G-II),and Graphene/SWCNT-COOH(Carboxylic-acid functionalized Single-walled Carbon Nanotubes)/PDMS(G-III). Each group had thirteen electrodes with varying concentrations ranging from 0.1-5wt%. Since CNTs get tangled easily, it becomes necessary to disperse them properly. To achieve optimal dispersion, CNTs were first sonicated with Isopropyl Alcohol (IPA), and then with PDMS. Mold casting was the technique used for fabricating the electrodes. The results were compared with the conventional ECG electrodes. Best results were achieved from G-III at 3wt% as the value of capacitance is high (0.172nF) as compared to G-I and G-III values at 3wt% which are 0.036nF (0.036nF) and 0.015nF respectively. As capacitance has an inverse relationship with the resistance and impedance, thus at 3wt% the resistance (0.361MΩ) and impedance (0.36MΩ) values are low, which satisfies the relationship. The values of resistance and impedance of G-II are low when compared with the values of G-I and G-II. Great results and ECG waveform are achieved with 3wt% for G-II, which also uses less nanomaterials to produce such great ECG results. It was observed that even after using the electrodes for 5 days, the ECG signal did not degrade over time and no skin allergies were detected for any of the three groups. The ECG tracking system was developed on the concept of the Internet-of-Things (IoT) using various electronic hardware components and software solutions. The results from the fabricated electrodes were promising and were suitable for long-term, and continuous ECG monitoring.

Hybrid, dual visible and near-infrared fluorescence emission of (6,5) single-walled carbon nanotubes modified with fluorescein through aryl diazonium salt chemistry.

The aryl diazonium salt chemistry offers enhancement of near-infrared (NIR) emission of single-walled carbon nanotubes (SWCNTs), although, the attachment of functional molecules which could bring hybrid properties through the process is underdeveloped. In this work, we utilize aryl diazonium salt of fluorescein to createsp3defects on (6,5) SWCNTs. We study the influence of pH on the grafting process identifying that pH 5-6 is necessary for a successful reaction. The fluorescein-modified (6,5) SWCNTs (F-(6,5) SWCNTs) exhibit red-shiftedE11* emission in the NIR region attributed to luminescentsp3defects, but also visible (Vis) fluorescence at 515 nm from surface-attached fluorescein molecules. The fluorescence in both Vis and NIR regions of F-(6,5) SWCNTs exhibit strong pH-dependency associated with the dissociation of fluorescein molecules with an indication of photoinduced-electron transfer quenching the Vis emission of fluorescein dianion. The F-(6,5) SWCNTs could potentially be used for dual-channel medical imaging as indicated by our preliminary experiments. We hope that our research will encourage new, bold modifications of SWCNTs with functional molecules introducing new, unique hybrid properties.

Surfactant Chemistry and Polymer Choice Affect Single-Wall Carbon Nanotube Extraction Conditions in Aqueous Two-Polymer Phase Extraction.

Quantitative determination of the effects of surfactant chemistry and polymer chain length on the concentration conditions necessary to yield extraction of specific single-wall carbon nanotube (SWNCT) species in an aqueous two-polymer phase extraction (ATPE) separation are reported. In particular, the effects of polyethylene glycol (PEG) chain length, surfactant ratios, and systematic structural variations of alkyl surfactants and bile salts on the surfactant ratios necessary for extraction were investigated using a recently reported fluorescence-based method. Alkyl surfactant tail length was observed to strongly affect the amount of surfactant necessary to cause PEG-phase extraction of nanotube species in ATPE, while variation in the anionic sulfate/sulfonate head group chemistry has less impact on the concentration necessary for extraction. Substitution of different bile salts results in different surfactant packings on the SWCNTs, with substitution greatly affecting the alkyl surfactant concentrations required for (n,m) extraction. Finally, distinct alkyl-to-bile surfactant ratios were found to extract specific (n,m) SWCNTs across the whole effective window of absolute concentrations, supporting the hypothesized competitive adsorption mechanism model of SWCNT sorting. Altogether, these results provide valuable insights into the underlying mechanisms behind ATPE-based SWCNT separations, towards further development and optimization of the ATPE method for SWCNT chirality and handedness sorting.

18ß-Glycyrrhetinic acid monoglucuronide (GAMG) alleviates single-walled carbon nanotubes (SWCNT)-induced lung inflammation and fibrosis in mice through PI3K/AKT/NF-κB signaling pathway.

Carbon nanotubes (CNTs) have become far and wide used in a number of technical and merchant applications as a result of substantial advances in nanotechnology, therein single-walled carbon nanotubes (SWCNT) are one of the most promising nanoparticles. Inhaling CNTs has been linked to a variety of health problems, including lung fibrosis. Glycyrrhetinic acid 3-O-mono-ß-D-glucuronide (GAMG), a natural sweetener, has anti-inflammatory and antioxidant capacities. The purpose of this study was to evaluate the potential for GAMG to alleviate SWCNT-induced lung inflammation and fibrosis. During days 3-28 after SWCNT intratracheal administration, we observed a remarkable increase of IL-1ß, IL-6 and TNF-α in bronchoalveolar lavage fluid (BALF) on day 3 and collagen deposition on day 28. GAMG treatment remarkably ameliorated SWCNT-induced pulmonary fibrosis and attenuated SWCNT-induced inflammation and collagen deposition, and suppressed the activation of PI3K/AKT/NF-κB signaling pathway in the lungs. Therefore, GAMG has a therapeutic potential for the treatment of SWCNT-induced pulmonary fibrosis. Targeting PI3K/AKT/NF-κB signaling pathway may be a potential therapeutic approach to treat pulmonary fibrosis in mice with SWCNT.

Fullerene Derivatives (CN-[OH]ß) and Single-Walled Carbon Nanotubes Modelled as Transporters for Doxorubicin Drug in Cancer Therapy.

Carbon nanomaterials have received increasing attention in drug-delivery applications because of their distinct properties and structures, including large surface areas, high conductivity, low solubility in aqueous media, unique chemical functionalities, and stability at the nano-scale size. Particularly, they have been used as nano-carriers and mediators for anticancer drugs such as Cisplatin, Camptothecin, and Doxorubicin. Cancer has become the most challenging disease because it requires sophisticated therapy, and it is classified as one of the top killers according to the World Health Organization records. The aim of the current work is to study and investigate the mechanism of combination between single-walled carbon nanotubes (SWCNTs) and fullerene derivatives (CN-[OH]ß) as mediators, and anticancer agents for photodynamic therapy directly to destroy the infected cells without damaging the normal ones. Here, we obtain a bio-medical model to determine the efficiency of the usefulness of Doxorubicin (DOX) as an antitumor agent conjugated with SWCNTs with variant radii r and fullerene derivative (CN-[OH]ß). The two sub-models are obtained mathematically to evaluate the potential energy arising from the DOX-SWCNT and DOX-(CN-[OH]ß) interactions. DOX modelled as two-connected spheres, small and large, each interacting with different SWCNTs (variant radii r) and fullerene derivatives CN-[OH]ß, formed based on the number of carbon atoms (N) and the number of hydroxide molecules (OH) (ß), respectively. Based on our obtained results, we find that the most favorable carbon nanomaterial is the SWCNT (r = 15.27 Å), followed by fullerene derivatives CN-(OH)22, CN-(OH)20, and CN-(OH)24, with minimum energies of -38.27, -33.72, -32.95, and -29.11 kcal/mol.

Covalent conjugation of single-walled carbon nanotube with CYP101 mutant for direct electrocatalysis.

Covalent linkage between the single-walled carbon nanotube (SWCNT) and CYP101 through a specific site of the enzyme can provide a novel method of designing efficient enzyme electrodes using this prototype cytochrome P450 enzyme. We have chemically modified the SWCNT with linker 4-carboxy phenyl maleimide (CPMI) containing maleimide functional groups. The enzyme was covalently attached on to the SWCNT through the maleimide group of the linker (CPMI) to the thiolate group of the surface exposed Cys 58 or Cys 136 of the CYP101 forming a covalently immobilized protein on the nanotube. Thin film of the modified SWCNT-CPMI-CYP101conjugate was made on a glassy carbon (GC) electrode. Direct electrochemistry of the substrate (camphor)-bound enzyme was studied using this immobilized enzyme electrode system and the redox potential was found to be -320mV vs Ag/AgCl (3 M KCl), which agrees with the redox potential of the substrate bound enzyme reported earlier. The electrochemically driven enzymatic mono-oxygenation of camphor by this immobilized enzyme electrode system was studied by measurement of the catalytic current at different concentrations of camphor. The catalytic current was found to increase with increasing concentration of camphor in presence of oxygen. The product formed during the catalysis was identified by mass-spectrometry as hydroxy-camphor.

The unpredictable carbon nanotube biocorona and a functionalization method to prevent protein biofouling.

BACKGROUND: The intrinsic physicochemical properties of carbon nanotubes (CNTs) make them unique tools in nanotechnology. Their elemental composition, resilience, thermal properties, and surface reactivity make CNTs also of undisputed interest in biotechnology. In particular, their extraordinary ability to capture biomolecules on their surface makes them essential in this field. The proteins adsorbed on the CNTs create a biological coating that endows them the ability to interact with some cell receptors, penetrate membranes or interfere with cell biomechanics, thus behaving as an active bio-camouflage. But some of these proteins unfold, triggering an immune response that unpredictably changes the biological activity of CNTs. For this reason, the control of the biocorona is fundamental in the nanobiotechnology of CNTs. RESULTS: Using TEM and AFM here we demonstrate a significant increase in CNTs diameter after protein functionalization. A quantitative analysis using TGA revealed that between 20 and 60% of the mass of functionalized nanotubes corresponds to protein, with single-walled CNTs capturing the highest amounts. To qualitatively/quantitatively characterize these biocoatings, we studied the biochemical "landscape" of the proteins captured by the different nanotubes after functionalization under various conditions. This study revealed a significant variability of the proteins in the corona as a function of the type of nanotube, the functionalization temperature, or the time after exposure to serum. Remarkably, the functionalization of a single type of CNT with sera from various human donors also resulted in different protein landscapes. Given the unpredictable assortment of proteins captured by the corona and the biological implications of this biocoating, we finally designed a method to genetically engineer and produce proteins to functionalize nanotubes in a controlled and customizable way. CONCLUSIONS: We demonstrate the high unpredictability of the spontaneous protein corona on CNTs and propose a versatile functionalization technique that prevents the binding of nonspecific proteins to the nanotube to improve the use of CNTs in biomedical applications.

Snapshots of the Fragmentation for C70@Single-Walled Carbon Nanotube: Tight-Binding Molecular Dynamics Simulations.

In previously reported experimental studies, a yield of double-walled carbon nanotubes (DWCNTs) at C70@Single-walled carbon nanotubes (SWCNTs) is higher than C60@SWCNTs due to the higher sensitivity to photolysis of the former. From the perspective of pyrolysis dynamics, we would like to understand whether C70@SWCNT is more sensitive to thermal decomposition than C60@SWCNT, and the starting point of DWCNT formation, which can be obtained through the decomposition fragmentation of the nanopeapods, which appears in the early stages. We have studied the fragmentation of C70@SWCNT nanopeapods, using molecular dynamics simulations together with the empirical tight-binding total energy calculation method. We got the snapshots of the fragmentation structure of carbon nano-peapods (CNPs) composed of SWCNT and C70 fullerene molecules and the geometric spatial positioning structure of C70 within the SWCNT as a function of dynamics time (for 2 picoseconds) at the temperatures of 4000 K, 5000 K, and 6000 K. In conclusion, the scenario in which C70@SWCNT transforms to a DWCNT would be followed by the fragmentation of C70, after C70, and the SWCNT have been chemically bonding in the early stages. The relative stability of fullerenes in CNPs could be reversed, compared to the ranking of the relative stability of the encapsulated molecules themselves.

Colorimetric strategy for ascorbic acid detection based on the oxidase-like activity of silver nanoparticle single-walled carbon nanotube composites.

A colorimetric assay for the determination and quantification of ascorbic acid (AA) is presented using silver nanoparticle (AgNP) single-walled carbon nanotube (AgNP/SWCNT) nanocomposites prepared using a microwave-assisted method. The AgNP/SWCNT nanocomposites possessed oxidase-like properties toward 3,3',5,5'-tetramethylbenzidine (TMB) and could catalyze the oxidation of TMB to form a blue oxidation product (λmax = 652 nm) in the absence of H2 O2 . AA can specifically inhibit the oxidation of TMB, resulting in a decline of the absorbance value and blue colour fading. As such, amounts of AA can be assessed easily by the unaided eye and quantitatively using an ultraviolet-visible light spectrophotometer. Under the optimal reaction conditions, this strategy showed a good linearity ranging from 0.4 µM to 5.0 µM for AA detection, and the limit of detection was 130 nM. This assay was also applied for AA measurement in vitamin C tablets and juice samples that yielded satisfactory results.

Highly Sensitive E-Textile Strain Sensors Enhanced by Geometrical Treatment for Human Monitoring.

Electronic textiles, also known as smart textiles or smart fabrics, are one of the best form factors that enable electronics to be embedded in them, presenting physical flexibility and sizes that cannot be achieved with other existing electronic manufacturing techniques. As part of smart textiles, e-sensors for human movement monitoring have attracted tremendous interest from researchers in recent years. Although there have been outstanding developments, smart e-textile sensors still present significant challenges in sensitivity, accuracy, durability, and manufacturing efficiency. This study proposes a two-step approach (from structure layers and shape) to actively enhance the performance of e-textile strain sensors and improve manufacturing ability for the industry. Indeed, the fabricated strain sensors based on the silver paste/single-walled carbon nanotube (SWCNT) layers and buffer cutting lines have fast response time, low hysteresis, and are six times more sensitive than SWCNT sensors alone. The e-textile sensors are integrated on a glove for monitoring the angle of finger motions. Interestingly, by attaching the sensor to the skin of the neck, the pharynx motions when speaking, coughing, and swallowing exhibited obvious and consistent signals. This research highlights the effect of the shapes and structures of e-textile strain sensors in the operation of a wearable e-textile system. This work also is intended as a starting point that will shape the standardization of strain fabric sensors in different applications.

No2 Sensing with SWCNT Decorated by Nanoparticles in Temperature Pulsed Mode: Modeling and Characterization.

In this paper, NO2 sensing by means of single-wall carbon nanotubes (SWCNT) networks, decorated with nanoparticles of TiO2 and Au, is proposed. In particular, it is shown that the performance of these materials can be enhanced using pulsed temperature mode. This sensing strategy effectiveness is theoretically and experimentally assessed. In this paper, in fact, a dynamic model for conductive gas sensors formed by networks of nanowires, considering the junctions between different wires as the main contribution to sensor conductance, and in the presence of the target gas, is presented and validated. The model accounts for variable temperature and gas concentration and sheds some light on the mechanisms leading to the sensor response improvement related to temperature pulsed working mode. It is also shown how the addition of a different material can be modeled through different surface adsorption kinetics.

Unprecedented New Crystalline Forms of SnSe in Narrow to Medium Diameter Carbon Nanotubes.

We report the observation of four unprecedented new crystalline forms of SnSe, obtained as a result of encapsulation in narrow to medium diameter single-walled carbon nanotubes. Aberration-corrected scanning transmission electron microscopy at 80 kV revealed linear, zigzag, helical (i.e., 2 × 1) atomic chains and a new form of encapsulated SnSe. This new form is apparently isostructural to free-standing MoS, MoSe, and WSe extreme nanowires etched from the corresponding monolayer dichalcogenides and also recently observed encapsulated MoTe. A structural model has been attained from annular dark-field (ADF) images. The experimental imaging agrees well with image simulations produced from models anticipated for the new structural forms.