A Bi2Te3 topological insulator/carbon nanotubes hybrid composites as a new counter electrode material for DSSC and NIR photodetector application.

Two-dimensional layered bismuth telluride (Bi2Te3), a prominent topological insulator, has garnered global scientific attention for its unique properties and potential applications in optoelectronics and electrochemical devices. Notably, there is a growing emphasis on improving photon-to-electron conversion efficiency in dye-sensitized solar cells (DSSCs), prompting the exploration of alternatives to noble metal catalysts like platinum (Pt). This study presents the synthesis of Bi2Te3 and its hybrid nanostructure with single-wall carbon nanotubes (SWCNT) via a straightforward hydrothermal process. The research unveils a novel application for the Bi2Te3-SWCNT hybrid structure, serving as a counter electrode in platinum-free DSSCs, facilitating the conversion of triiodide (I3-) to iodide (I-) and functioning as an active electrode material in a photodetector (n-Bi2Te3-SWCNT/p-Si). The resulting DSSC employing the Bi2Te3-SWCNT hybrid counter electrode achieves a power conversion efficiency (PCE) of 4.2 %, a photocurrent density of 10.5 mA/cm2, a fill factor (FF) of 62 %, and superior charge transfer kinetics compared to pristine Bi2Te3 based counter electrode (PCE 2.1 %, FF 34 %). Additionally, a spin coating technique enhances the performance of the n-Bi2Te3-SWCNT/p-Si photodetector, yielding a responsivity of 2.2 AW-1, detectivity of 1.2 × 10-3 and enhanced external quantum efficiency. These findings demonstrate that the newly developed Bi2Te3-SWCNT heterostructure enhances interfacial charge transport, electrocatalytic performance in DSSCs, and overall photodetector performance.

Orthogonal Determination of Competing Surfactant Adsorption onto Single-Wall Carbon Nanotubes During Aqueous Two-Polymer Phase Extraction via Fluorescence Spectroscopy and Analytical Ultracentrifugation.

A combination of analytical ultracentrifugation (AUC) and fluorescence spectroscopy are utilized to orthogonally probe compositions of adsorbed surfactant layers on the surface of (7,5) species single-wall carbon nanotubes (SWCNTs) under conditions known to achieve differential partitioning in aqueous two-phase extraction (ATPE) separations. Fluorescence emission intensity and AUC anhydrous particle density measurements independently probe and can discriminate between adsorbed surfactant layers on a (7,5) nanotube comprised of either of two common nanotube dispersants, the anionic surfactants sodium deoxycholate and sodium dodecyl sulfate. Measurements on dispersions containing mixtures of both surfactants indicate near total direct exchange of the dominant surfactant species adsorbed to the carbon nanotube at a critical concentration ratio consistent with the ratio leading to partitioning change in the ATPE separation. By conducting these orthogonal measurements in a complex environment reflective of an ATPE separation, including multiple surfactant and polymer solution components, the results provide direct evidence for the hypothesis that it is the nature of the adsorbed surfactant layer that primarily controls partitioning behavior in selective ATPE separations of SWCNTs.

Noninvasive Injectable Optical Nanosensor-Hydrogel Hybrids Detect Doxorubicin in Living Mice.

While the tissue-transparent fluorescence of single-walled carbon nanotubes (SWCNTs) imparts substantial potential for use in non-invasive biosensors, development of non-invasive systems is yet to be realized. Here, we investigated the functionality of a SWCNT-based nanosensor in several injectable SWCNT-hydrogel systems, ultimately finding SWCNT encapsulation in a sulfonated methylcellulose hydrogel optimal for detection of ions, small molecules, and proteins. We found that the hydrogel system and nanosensor signal were stable for several weeks in live mice. We then found that this system successfully detects local injections of the chemotherapeutic agent doxorubicin in mice. We anticipate future studies to adapt this device for detection of other analytes in animals and, ultimately, patients.

High Spatiotemporal Precision Mapping of Optical Nanosensor Array Using Machine Learning.

Optical nanosensors, including single-walled carbon nanotubes (SWCNTs), provide real-time spatiotemporal reporting at the single-molecule level within a nanometer-scale area. However, their superior sensitivity also makes them susceptible to slight environmental influences such as reference analytes in media, external fluid flow, and mechanical modulations. Consequently, they often fail to achieve the optimal limit of detection (LOD) and frequently convey misinformation spatiotemporally. To address this challenge, we developed a single-pixel mapping technique for optical nanosensor arrays that operates with high spatiotemporal precision using machine learning. We systematically measured the spatial sensing images of various analyte concentrations below the LOD by using a near-infrared (nIR) fluorescent SWCNT nanosensor array. For dopamine (DA) as an example analyte, we extracted single-pixel level sensing features such as entropy, the Laplacian operator, and neighboring values under noise levels. We then trained the artificial intelligence (AI) model to accurately identify specific reaction pixels of the nanosensor array, even below the LOD region. Additionally, our method can distinguish subtle noise caused by fluid in the media or mechanical modulation of the array substrate. As a result, our approach significantly improved the detection sensitivity of the nanosensor array, achieving a 13-fold increase over the original LOD and halving the detection time of the reporter pixels, with F1 scores exceeding 0.9. This method not only lowers the LOD of optical nanosensors but also isolates sensor responses specific to the analyte, providing accurate spatiotemporal information to the user, even in noisy conditions. It can be universally applied to various optical nanosensor materials and analytes, maximizing the sensitivity and accuracy of the nanosensors used in diagnostics and analysis.

Duffy Antigen Receptor for Chemokines (DARC) Nanodisc-Based Biosensor for Detection of Staphylococcal Bicomponent Pore-Forming Leukocidins.

Staphylococcus aureus (S. aureus) is an opportunistic infectious pathogen, which causes a high mortality rate during bloodstream infections. The early detection of virulent strains in patients' blood samples is of medical interest for rapid diagnosis. The main virulent factors identified in patient isolates include leukocidins that bind to specific membrane receptors and lyse immune cells and erythrocytes. Duffy antigen receptor for chemokines (DARC) on the surface of specific cells is a main target of leukocidins such as gamma-hemolysin AB (HlgAB) and leukocidin ED (LukED). Among them, HlgAB is a conserved and critical leukocidin that binds to DARC and forms pores on the cell membranes, leading to cell lysis. Current methods are based on ELISA or bacterial culture, which takes hours to days. For detecting HlgAB with faster response and higher sensitivity, we developed a biosensor that combines single-walled carbon nanotube field effect transistors (swCNT-FETs) with immobilized DARC receptors as biosensing elements. DARC was purified from a bacterial expression system and successfully reconstituted into nanodiscs that preserve binding capability for HlgAB. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) showed an increase of the DARC-containing nanodisc size in the presence of HlgAB, indicating the formation of HlgAB prepore or pore complexes. We demonstrate that this sensor can specifically detect the leukocidins HlgA and HlgAB in a quantitative manner within the dynamic range of 1 fM to 100 pM with an LOD of 0.122 fM and an LOQ of 0.441 fM. The sensor was challenged with human serum spiked with HlgAB as simulated clinical samples. After dilution for decreasing nonspecific binding, it selectively detected the toxin with a similar detection range and apparent dissociation constant as in the buffer. This biosensor was demonstrated with remarkable sensitivity to detect HlgAB rapidly and has the potential as a tool for fundamental research and clinical applications, although this sensor cannot differentiate between HlgAB and LukED as both have the same receptor.

Sequential Cascade Doping of Conjugated-Polymer-Wrapped Carbon Nanotubes for Highly Electrically Conductive Platforms.

To explore a highly conductive flexible platform, this study develops PIDF-BT@SWCNT by wrapping single-walled carbon nanotubes (SWCNTs) with a conjugated polymer, PIDF-BT, known for its effective doping properties. By evaluating the doping behaviors of various dopants on PIDF-BT, appropriate dopant combinations for cascade doping are selected to improve the doping efficiency of PIDF-BT@SWCNT. Specifically, using F4TCNQ or F6TCNNQ as the first dopant, followed by AuCl3 as the second dopant, demonstrates remarkable doping efficiency, surpassing that of the individual dopants and yielding an exceptional electrical conductivity exceeding 6000 S/cm. Characterization using X-ray photoelectron spectroscopy and Raman spectroscopy elucidates the doping mechanism, revealing an increase in the proportion of electron-donating atoms and the ratio of quinoid structures upon F4TCNQ/AuCl3 cascade doping. These findings offer insights into optimizing dopant combinations for cascade doping, showcasing its advantages in enhancing doping efficiency and resulting electrical conductivity compared with single dopant processes.

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.

Optical Aptamer-Based Cytokine Nanosensor Detects Macrophage Activation by Bacterial Toxins.

Overactive or dysregulated cytokine expression is a hallmark of many acute and chronic inflammatory diseases. This is true for acute or chronic infections, neurodegenerative diseases, autoimmune diseases, cardiovascular diseases, cancer, and others. Cytokines such as interleukin-6 (IL-6) are known therapeutic targets and biomarkers for such inflammatory diseases. Platforms for cytokine detection are, therefore, desirable tools for both research and clinical applications. Single-walled carbon nanotubes (SWCNT) are versatile nanomaterials with near-infrared fluorescence that can serve as transducers for optical sensors. When functionalized with an analyte-specific recognition element, SWCNT emission may become sensitive and selective toward the desired target. SWCNT-aptamer sensors are easily assembled, inexpensive, and biocompatible. In this work, we introduced a nanosensor design based on SWCNT and a DNA aptamer specific to IL-6. We first evaluated several SWCNT-aptamer constructs based on this simple direct complexation method, wherein the aptamer both solubilizes the SWCNT and confers sensitivity to IL-6. The sensor limit of detection, 105 ng/mL, lies in the relevant range for pathological IL-6 levels. Upon investigation of sensor kinetics, we found rapid response within seconds of antigen addition which continued over the course of 3 h. We found that this sensor construct is stable and the aptamer is not displaced from the nanotube surface during IL-6 detection. Finally, we investigated the ability of this sensor construct to detect macrophage activation caused by bacterial lipopolysaccharides (LPS) in an in vitro model of disease, finding rapid and sensitive detection of macrophage-expressed IL-6. We are confident that further development of this sensor will have novel implications for diagnosis of acute and chronic inflammatory diseases, in addition to contributing to the understanding of the role of cytokines in these diseases.

Single-walled carbon nanotube-protein complex: A strategy to improve the immune response to protein in mice.

Vaccines represent an effective tool for controlling disease infection. As a key component of vaccines, many types of adjuvants have been developed and used today. This study is designed to investigate the efficacy of single-walled carbon nanotubes (SWCNTs) as a new adjuvant. The results showed that SWCNT could adsorb the antigen by intermolecular action, and the adsorption rate was significantly higher after dispersion of the SWCNTs in a sonic bath. The titer of specific antibody of mice in the SWCNTs group was higher than that of the mice in the antigen control group, confirming the adjuvant efficacy of SWCNTs. During immunisation, the specific antibody was detected earlier in the mice of the SWCNTs group, especially when the amount of antigen was reduced. And it was proved that the titer of antibodies was higher after subcutaneous and intraperitoneal injection compared to intramuscular injection. Most importantly, the mice immunised with SWCNTs showed almost the same level of immunity as the mice in the FCA (Freund's complete adjuvant) group, indicating that the SWCNTs were an effective adjuvant. In addition, the mice in the SWCNT group maintained antibody levels for 90 days after the last booster vaccination and showed a good state of health during the observed period. We also found that the SWCNTs were able to induce macrophages activation and enhance antigen uptake by mouse peritoneal macrophages.

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.

Optical Nanosensor Passivation Enables Highly Sensitive Detection of the Inflammatory Cytokine Interleukin-6.

Interleukin-6 (IL-6) is known to play a critical role in the progression of inflammatory diseases such as cardiovascular disease, cancer, sepsis, viral infection, neurological disease, and autoimmune diseases. Emerging diagnostic and prognostic tools, such as optical nanosensors, experience challenges in translation to the clinic in part due to protein corona formation, dampening their selectivity and sensitivity. To address this problem, we explored the rational screening of several classes of biomolecules to be employed as agents in noncovalent surface passivation as a strategy to screen interference from nonspecific proteins. Findings from this screening were applied to the detection of IL-6 by a fluorescent-antibody-conjugated single-walled carbon nanotube (SWCNT)-based nanosensor. The IL-6 nanosensor exhibited highly sensitive and specific detection after passivation with a polymer, poly-l-lysine, as demonstrated by IL-6 detection in human serum within a clinically relevant range of 25 to 25,000 pg/mL, exhibiting a limit of detection over 3 orders of magnitude lower than prior antibody-conjugated SWCNT sensors. This work holds potential for the rapid and highly sensitive detection of IL-6 in clinical settings with future application to other cytokines or disease-specific biomarkers.

Rational Design of 3D Polymer Corona Interfaces of Single-Walled Carbon Nanotubes for Receptor-Free Virus Recognition.

Facing the escalating threat of viruses worldwide, the development of efficient sensor elements for rapid virus detection has never been more critical. Traditional point-of-care (POC) sensors struggle due to their reliance on fragile biological receptors and limited adaptability to viral strains. In this study, we introduce a nanosensor design for receptor-free virus recognitions using near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWCNTs) functionalized with a poly(ethylene glycol) (PEG)-phospholipid (PEG-lipid) array. Three-dimensional (3D) corona interfaces of the nanosensor array enable selective and sensitive detection of diverse viruses, including Ebola, Lassa, H3N2, H1N1, Middle East respiratory syndrome (MERS), severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1), and SARS-CoV-2, even without any biological receptors. The PEG-lipid components, designed considering chain length, fatty acid saturation, molecular weight, and end-group moieties, allow for precise quantification of viral recognition abilities. High-throughput automated screening of the array demonstrates how the physicochemical properties of the PEG-lipid/SWCNT 3D corona interfaces correlate with viral detection efficiency. Utilizing molecular dynamics and AutoDock simulations, we investigated the impact of PEG-lipid components on 3D corona interface formation, such as surface coverage and hydrodynamic radius and specific molecular interactions based on chemical potentials. Our findings not only enhance detection specificity across various antigens but also accelerate the development of sensor materials for promptly identifying and responding to emerging antigen threats.

High-sensitivity and energy-efficient chloride ion sensors based on flexible printed carbon nanotube thin-film transistors for wearable electronics.

The advent of flexible single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) has transformed electronics, providing significant benefits like low operating voltage, reduced power consumption, cost-effectiveness, and improved signal amplification. This study focuses on leveraging these attributes to develop a novel flexible high-sensitivity and energy-efficient chloride ion sensors based on printed flexible SWCNT-TFTs utilizing polymers-sorted semiconducting SWCNTs (sc-SWCNTs) as the active layers and ion liquids-poly(4-vinylphenol as dielectric layers along with the evaporated deposition of aluminum electrodes and printed silver electrodes as the gate and source-drain electrodes, respectively. The sensors exhibit several operational advantages, including low voltage requirements (≤1 V), rapid response speed (5.32 s), significant signal amplification (Up to 702.6 %), low power consumption (0.31 µJ at 1 mmol chloride ion), good repeatability, high sensitivity for both low and high concentrations of chloride ion (up to 100 mmol/L) and excellent mechanical flexibility (No obvious changes after bending for 10,000 times with a 5 mm radius). The detection mechanism of chloride ions was analyzed using X-ray Photoelectron Spectroscopy (XPS). It was found that chloride ions react with silver nanoparticles (AgNPs) to form silver chloride (AgCl) on printed electrodes, impeding carrier transport and reducing the currents in SWCNT TFTs. Importantly, our sensors' compatibility with smart devices allows for real-time monitoring of chloride ion levels in human sweat, offering significant potential for daily health monitoring.

Analysis of Soret and Dufour effects on radiative heat transfer in hybrid bioconvective flow of carbon nanotubes.

Numerous heat transfer applications, such as heat exchangers, solar trough collectors, and fields including food processing, material research, and aerospace engineering, utilize hybrid nanofluids. Compared to conventional fluids, hybrid nanofluids exhibit significantly enhanced thermal conductivity. The aim of this work is to explore flow and heat transmission features under of magneto-hydrodynamic bioconvective flow of carbon nanotubes over the stretched surface with Dufour and Soret effects. Additionally, comparative dynamics of the carbon nanotubes (SWCMT - MWCNT/C2H6O2 with SWCMT - MWCNT/C2H6O2 - H2O) flow using the Prandtl fluid model in the presence of thermal radiation and motile microorganisms has been investigated. Novel feature Additionally, the focus is also to examine the presence of microorganisms in mixture base hybrid nanofluid. To examine heat transfer features of Prandtl hybrid nanofluid over the stretched surface convective heating is taken into consideration while modeling the boundary conditions. Suitable similarity transform has been employed to convert dimensional flow governing equations into dimensionless equations and solution of the problem has been obtained using effective, accurate and time saving bvp-4c technique in MATLAB. Velocity, temperature, concentration and microorganisms profiles have been demonstrated graphically under varying impact of various dimensionless parameters such as inclined magnetization, mixed convection, Dufour effect, Soret effect, thermal radiation effect, and bioconvection lewis number. It has been observed that raising values of magnetization (0.5 ≤ M ≤ 4), mixed convection (0.01 ≤ λ ≤ 0.05) and inclination angle (0° ≤ α ≤ 180°) enhance fluid motion rapidly in Ethylene glycol based Prandtl hybrid nanofluid (SWCMT - MWCNT/C2H6O2) when compared with mixture base working fluid of carbon nanotubes SWCMT - MWCNT/C2H6O2 - H2O). Raising thermal radiation (0.1 ≤ Rd ≤ 1.7) and Dufour number (0.1 ≤ Du ≤ 0.19) values improves temperature profile. Moreover, a good agreement has been found between the current outcome and existing literature for skin friction outcomes.

An optical aptamer-based cytokine nanosensor detects macrophage activation by bacterial toxins.

Overactive or dysregulated cytokine expression is hallmark of many acute and chronic inflammatory diseases. This is true for acute or chronic infection, neurodegenerative diseases, autoimmune diseases, cardiovascular disease, cancer, and others. Cytokines such as interleukin-6 (IL-6) are known therapeutic targets and biomarkers for such inflammatory diseases. Platforms for cytokine detection are therefore desirable tools for both research and clinical applications. Single-walled carbon nanotubes (SWCNT) are versatile nanomaterials with near-infrared fluorescence that can serve as transducers for optical sensors. When functionalized with an analyte-specific recognition element, SWCNT emission may become sensitive and selective towards the desired target. SWCNT-aptamer sensors are easily assembled, inexpensive, and biocompatible. In this work, we introduced a nanosensor design based on SWCNT and a DNA aptamer specific to IL-6. We first evaluated several SWCNT-aptamer constructs based on this simple direct complexation method, wherein the aptamer both solubilizes the SWCNT and confers sensitivity to IL-6. The sensor limit of detection, 105 ng/mL, lies in the relevant range for pathological IL-6 levels. Upon investigation of sensor kinetics, we found rapid response within seconds of antigen addition which continued over the course of three hours. We found that this sensor construct is stable, and the aptamer is not displaced from the nanotube surface during IL-6 detection. Finally, we investigated the ability of this sensor construct to detect macrophage activation caused by bacterial lipopolysaccharides (LPS) in an in vitro model of disease, finding rapid and sensitive detection of macrophage-expressed IL-6. We are confident further development of this sensor will have novel implications for diagnosis of acute and chronic inflammatory diseases, in addition to contributing to the understanding of the role of cytokines in these diseases.

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.

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.

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.

A novel olfactory biosensor based on ZIF-8@SWCNT integrated with nanosome-AuNPs/Prussian blue for sensitive detection of hexanal.

Hexanal is considered as an important volatile compound indicator for the assessment of freshness and maturity of foods. Therefore, sensitive and stable monitoring of hexanal is highly desired. Herein, an efficient receptor immobilization strategy based on ZIF-8@ Single-walled carbon nanotube (SWCNT) and nanosomes-AuNPs/Prussian blue (PB) was proposed for the development of olfactory biosensors. ZIF-8@SWCNT as dual support materials provided a high density of active sites for nanosomes loading. Moreover, the co-electrodeposition of nanosomes-AuNPs and PB on the sensor interface effectively amplified the electrochemical signal and maintained the activity of the receptor. The combination of ZIF-8@SWCNT with AuNPs/PB imparts excellent sensing performance of the biosensor with a wide detection range of 10-16-10-9 M, a low detection limit of 10-16 M for hexanal, and a long storage stability of 15 days. These results indicate that our biosensor can be a powerful tool for versatile applications in food and other related industries.

Single-Molecule Methane Sensing Using Palladium-Functionalized nIR Fluorescent Single-Walled Carbon Nanotubes.

There has been considerable interest in detecting atmospheric and process-associated methane (CH4) at low concentrations due to its potency as a greenhouse gas. Nanosensor technology, particularly fluorescent single-walled carbon nanotube (SWCNT) arrays, is promising for such applications because of their chemical sensitivities at single-molecule detection limits. However, the methodologies for connecting the stochastic molecular fluctuations from gas impingement on such sensors require further development. In this work, we synthesize Pd-conjugated ss(GT)15-DNA-wrapped SWCNTas near-infrared (nIR) fluorescent, single-molecule sensors of CH4. The complexes are characterized using X-ray photoelectron spectroscopy (XPS) and spectrophotometry, demonstrating spectral changes between the Pd2+ and Pd0 oxidation states. The nIR fluctuations generated upon exposure from 8 to 26 ppb of CH4 were separated into high- and low-frequency components. Aggregating the low-frequency components for an array of sensors showed the most consistent levels of detection with a limit of 0.7 ppb. These results advance the hardware and computational methods necessary to apply this approach to the challenge of environmental methane sensing.