Electrical Transport and Dynamics of Confined DNA through Highly Conductive 2D Graphene Nanochannels

Confining DNA in nanochannels is an important approach to studying its structure and transportation dynamics. Graphene nanochannels are particularly attractive for studying DNA confinement due to their atomic flatness, precise height control, and excellent mechanical strength. Here, using femtosecond laser etching and wetting transfer, we fabricate graphene nanochannels down to less than 4.3 nm in height, with the length-to-height ratios up to 103. These channels exhibit high stability, low noise, and self-cleaning ability during the long-term ionic current recording. We report a clear linear relationship between DNA length and the residence time in the channel and further utilize this relationship to differentiate DNA fragments based on their lengths, ranging widely from 200 bps to 48.5 kbps. The graphene nanochannel presented here provides a potential platform for label-free analyses and reveals fundamental insights into the conformational dynamics of DNA and proteins in confined space.

Highly Conductive, Ultrastrong, and Flexible Wet-Spun PEDOT:PSS/Ionic Liquid Fibers for Wearable Electronics

Conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fibers with high electrical conductivity, flexibility, and robustness are urgently needed for constructing wearable fiber-based electronics. In this study, the highly conductive (4288 S/cm), ultrastrong (a high tensile strength of 956 MPa), and flexible (a low Young's modulus of 3.8 GPa) PEDOT:PSS/1-ethyl-3-methylimidazolium dicyanamide (EMIM:DCA) (P/ED) fiber was prepared by wet-spinning and a subsequent H₂SO₄-immersion-drawing process. As far as we know, this is the best performance of the PEDOT:PSS fiber reported so far. The structure and conformation of the P/ED fiber were characterized by FESEM, XPS, Raman spectroscopy, UV-vis-NIR spectroscopy, and WAXS. The results show that the high performances of the P/ED fiber are mainly attributed to the massive removal of PSS and high degree of crystallinity (87.9%) and orientation (0.71) of PEDOT caused by the synergistic effect of the ionic liquid, concentrated sulfuric acid, and high stretching. Besides, the P/ED fiber shows a small bending radius of 0.1 mm, and the conductivity of the P/ED fiber is nearly unchanged after 1000 repeated cycles of bending and humidity changes within 50-90%. Based on this, various P/ED fiber-based devices including the circuit connection wire, thermoelectric power generator, and temperature sensor were constructed, demonstrating its wide applications for constructing flexible and wearable electronics.

Conductive Al-Doped ZnO Framework Embedded with Catalytic Nanocages as a Multistage-Porous Sulfur Host in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries possess many practical challenges including the lithium polysulfide (LiPS) "shuttle effect" and their sluggish conversion kinetics. To address these issues, a unique hierarchical porous architecture, combining highly conductive ordered macroporous skeleton and embedded microporous particles is rationally designed as a dual-effective polysulfide immobilizer and conversion promoter. In this nanoporous architecture, Al-doped ZnO (AZO) acts as a conductive macroporous framework, profiting chemical anchoring of LiPS as well as facilitating electrolyte infiltration and ion diffusion; Co nanoparticle-anchored N-doped carbon (Co-NC) derived from CoZn-metal-organic framework is embedded in the macropores to further strengthen the LiPS adsorption, catalytically accelerating conversion kinetics of LiPS simultaneously. Consequently, the Co-NC@AZO/S cathode delivers a notable rate capability of 635.5 mA h g^-1 at 5 C. A high area capacity of about 5.8 mA h cm^-2 with a mass loading of 6.8 mg cm^-2 is also achieved under a lean electrolyte (E/S = 5.7). Additionally, the Li-S pouch cells equipped with Co-NC@AZO can be extended to sulfur loading as high as 4.0 mg cm^-2, delivering a superb capability of 897.5 mA h g^-1 after 100 cycles. This work puts forward a design for stably cycled and practically viable Li-S batteries.

Underwater, Multifunctional Superhydrophobic Sensor for Human Motion Detection

Superhydrophobic conductive materials have received a great amount of interest due to their wide applications in oil-water separation, electrically driven smart surface, electromagnetic shielding, and body motion detection. Herein, a highly conductive superhydrophobic cotton cloth is prepared by a facile method. A layer of polydopamine/reduced graphene oxide (PDA/rGO) was first coated on the cotton fabric, and then copper nanoparticles were in situ grown on the prepared surface. After further modification with stearic acid (STA), the wettability of the cotton surface changed from superhydrophilic to superhydrophobic (water contact angle (WCA) = 153°). The electrical conductivity of the PDA/rGO/Cu/STA cotton is as high as 6769 S·m^-1, while the stearic acid effectively protects Cu NPs from oxidation. As a result, the superhydrophobic PDA/rGO/Cu/STA cotton has shown excellent electrical stability and can be used in detecting human motions in both ambient and underwater conditions. The sensor can recognize human motion from air into water and other underwater activities (e.g., underwater bending, stretching, and ultrasound). This multifunctional cotton device can be used as an ideal sensor for underwater intelligent devices and provides a basis for further research.

Self-Cleaning, Chemically Stable, Reshapeable, Highly Conductive Nanocomposites for Electrical Circuits and Flexible Electronic Devices

Materials with multiple functions are highly desirable in practical applications. Developing multifunctional nanocomposites by a straightforward process is still a challenge. Here, a versatile nanocomposite has been developed by simple blending and pressing of multiwalled carbon nanotubes (MWCNTs) and modified polydimethylsiloxane (MPDMS). Because of the synergistic effect of MWCNTs and MPDMS, this nanocomposite exhibits outstanding hydrophobic property, striking self-cleaning capability, and excellent chemical stability against strong acid and strong base, which makes it possible to work under wet and even extreme chemical conditions. Besides, because of its flexibility, this nanocomposite can be reshaped, bended, twisted, and molded into on-demand patterns for special applications. Owing to the good distribution of MWCNTs, the nanocomposite shows high conductivity (with a sheet resistance of 86.33 Ω sq^-1) and high healing efficiency (above 96.53%) in an electrical field, and it also exhibits outstanding performance in various electrical circuits and flexible electroluminescent devices. Furthermore, the inherent portability, recyclability, and reusability of this nanocomposite make it more convenient and environmentally friendly for practical applications. Thus, our work provides a new strategy to develop a multifunctional nanocomposite, and it shows tremendous potential in flexible electronics.

Preparation of a Highly Conductive Seed Layer for Calcium Sensor Fabrication with Enhanced Sensing Performance

The seed layer plays a crucial role in achieving high electrical conductivity and ensuring higher performance of devices. In this study, we report fabrication of a solution-gated field-effect transistor (FET) sensor based on zinc oxide nanorods (ZnO NRs) modified iron oxide nanoparticles (α-Fe₂O₃ NPs) grown on a highly conductive sandwich-like seed layer (ZnO seed layer/Ag nanowires/ZnO seed layer). The sandwich-like seed layer and ZnO NRs modification with α-Fe₂O₃ NPs provide excellent conductivity and prevent possible ZnO NRs surface damage from low pH enzyme immobilization, respectively. The highly conductive solution-gated FET sensor employed the calmodulin (CaM) immobilization on the surface of α-Fe₂O₃-ZnO NRs for selective detection of calcium ions (Ca²⁺). The solution-gated FET sensor exhibited a substantial change in conductance upon introduction of different concentrations of Ca²⁺ and showed high sensitivity (416.8 μA cm^-2 mM^-1) and wide linear range (0.01-3.0 mM). In addition, the total Ca²⁺ concentration in water and serum samples was also measured. Compared to the analytically obtained data, our sensor was found to measure Ca²⁺ in the water and serum samples accurately, suggesting a potential alternative for Ca²⁺ determination in water and serum samples, specifically used for drinking/irrigation and clinical analysis.

Nitrogen-Superdoped 3D Graphene Networks for High-Performance Supercapacitors

An N-superdoped 3D graphene network structure with an N-doping level up to 15.8 at% for high-performance supercapacitor is designed and synthesized, in which the graphene foam with high conductivity acts as skeleton and nested with N-superdoped reduced graphene oxide arogels. This material shows a highly conductive interconnected 3D porous structure (3.33 S cm^-1 ), large surface area (583 m² g^-1 ), low internal resistance (0.4 Ω), good wettability, and a great number of active sites. Because of the multiple synergistic effects of these features, the supercapacitors based on this material show a remarkably excellent electrochemical behavior with a high specific capacitance (of up to 380, 332, and 245 F g^-1 in alkaline, acidic, and neutral electrolytes measured in three-electrode configuration, respectively, 297 F g^-1 in alkaline electrolytes measured in two-electrode configuration), good rate capability, excellent cycling stability (93.5% retention after 4600 cycles), and low internal resistance (0.4 Ω), resulting in high power density with proper high energy density.

Solution-Processed Highly Superparamagnetic and Conductive PEDOT:PSS/Fe3O4 Nanocomposite Films with High Transparency and High Mechanical Flexibility

Multifunctional films can have important applications. Transparent and flexible films with high conductivity and magnetic properties can be used in many areas, such as electromagnetic interference (EMI) shielding, magnetic switching, microwave absorption, and also biotechnology. Herein, novel highly conductive and superparamagnetic thin films with excellent transparency and flexibility have been demonstrated. The films were formed from a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS; Clevios PH1000) aqueous solution added with iron oxide (Fe₃O₄) nanoparticles that have a size of ∼20 nm by spin-coating. The PEDOT:PSS/Fe₃O₄ films have a high conductivity of 1080 S/cm through treatment with methylammonium iodide in an organic solvent. The high-conductivity PEDOT:PSS/Fe₃O₄ films can also have a saturation magnetization of 25.5 emu/g and an EMI shielding effectiveness of more than 40 dB in the 8-12.5 GHz (X band) frequency range. The PEDOT:PSS/Fe₃O₄ films have additional advantages, like excellent transparency, good mechanical flexibility, low cost, and light weight. In addition, we fabricate flexible PEDOT:PSS/Fe₃O₄ silk threads with a high magnetism and conductivity.