Charge Transport in 2D DNA Tunnel Junction Diodes

Recently, deoxyribonucleic acid (DNA) is studied for electronics due to its intrinsic benefits such as its natural plenitude, biodegradability, biofunctionality, and low‐cost. However, its applications are limited to passive components because of inherent insulating properties. In this report, a metal–insulator–metal tunnel diode with Au/DNA/NiO_x junctions is presented. Through the self‐aligning process of DNA molecules, a 2D DNA nanosheet is synthesized and used as a tunneling barrier, and semitransparent conducting oxide (NiO_x) is applied as a top electrode for resolving metal penetration issues. This molecular device successfully operates as a nonresonant tunneling diode, and temperature‐variable current–voltage analysis proves that Fowler–Nordheim tunneling is a dominant conduction mechanism at the junctions. DNA‐based tunneling devices appear to be promising prototypes for nanoelectronics using biomolecules.     

High-Performing Atomic Electrocatalyst for Chlorine Evolution Reaction

Electrocatalysts facilitating chlorine evolution reaction (ClER) play a vital role in chlor–alkali industries. Owing to a huge amount of chlorine consumed worldwide, inexpensive high-performing catalysts for Cl₂ production are highly demanded. Here, a superb ClER catalyst fabricated through uniform dispersion of Pt single atoms (SAs) in  C₂N₂ moieties of N-doped graphene (denoted as Pt-1) is presented, which demonstrates near 100% exclusive ClER selectivity, long-term durability, extraordinary Cl₂ production rate (3500 mmol h⁻¹ g_Pt⁻¹), and >140 000-fold increased mass activity over industrial electrodes in acidic medium. Excitingly, at the typical chlor–alkali industries’ operating temperature (80 °C), Pt-1 supported on carbon paper electrode requires a near thermoneutral ultralow overpotential of 5 mV at 1 mA cm⁻² current density to initiate the ClER, consistent with the predicted density functional theory (DFT) calculations. Altogether these results show the promising electrocatalyst of Pt-1 toward ClER.     

Switchable Xe/Kr Selectivity in a Hofmann-Type Metal–Organic Framework via Temperature-Responsive Rotational Dynamics

The development of adsorbents for Kr and Xe separation is essential to meet industrial demands and for energy conservation. Although a number of previous studies have focused on Xe-selective adsorbents, stimuli-responsive Xe/Kr-selective adsorbents still remain underdeveloped. Herein, a Hofmann-type framework Co(DABCO)[Ni(CN)₄] (referred to as CoNi-DAB ; DABCO = 1,4-diazabicyclo[2,2,2]octane) that provides a temperature-dependent switchable Xe/Kr separation performance is reported. CoNi-DAB showed high Kr/Xe (0.8/0.2) selectivity with significant Kr adsorption at 195 K as well as high Xe/Kr (0.2/0.8) selectivity with superior Xe adsorption at 298 K. Such adsorption features are associated with the temperature-dependent rotational configuration of the DABCO ligand, which affects the kinetic gate-opening temperature of Xe and Kr. The packing densities of Xe (2.886 g cm⁻³ at 298 K) and Kr (2.399 g  cm⁻³ at 195 K) inside the framework are remarkable and comparable with those of liquid Xe (3.057 g cm⁻³) and liquid Kr (2.413 g cm⁻³), respectively. Breakthrough experiments confirm the temperature-dependent reverse separation performance of CoNi-DAB at 298 K under dry and wet (88% relative humidity) conditions and at 195 K under dry conditions. The unique adsorption behavior is also verified through van der Waals (vdW)-corrected density functional theory (DFT) calculations and nudged elastic band (NEB) simulations.     

Fabrication of 3D structured composites of crumpled graphene,polyaniline and molybdenum disulfide nanosheets for high performance alkali metal ion storage

Recently, there is a growing concern for high performance energy storage devices in many applications where a lot of energy needs to be either stored or delivered. Here, we introduce a facile strategy to fabricate effectively combined 3D structured composites of crumpled graphene (CGR), polyaniline (PANI) and molybdenum disulfide (MoS₂) for potential application to high performance alkali metal ion storage such as sodium and lithium ion storage. 2D graphene oxides, polyaniline, and physically exfoliated 2D MoS₂ were combined to fabricate 3D structured CGR/PANI/MoS₂ composites by aerosol self-assembly process and post heat treatment. Overall morphology of composites looked like crumpled paper ball with an average diameter of ~5 μm. MoS₂ and PANI were attached on the surface of the graphene, which supported an accessible surface area and provided a path for electron transfer. Synergistic effect by the combination of the three functional materials resulted in outstanding electrochemical performance as sodium-ion storage in terms of storage capacity (328 F g^?1 at 1 A g^?1), good rate capability (282 F g^?1 at 10 A g^?1), and cycle performance (95%, after 1000 cycles). Even lithium-ion storage application, the CGR/PANI/MoS₂ also delivered a high specific capacity of 470 mAh g^?1 after 100 cycles.     

Effect of BN Coating on the Strength of a Mullite Type Fiber

Nextel 480 is a polycrystalline essentially mullite fiber (70 wt.-% Al₂O₃+28 wt.-% SiO₂+2 wt.-% B₂O₃). Different thicknesses of BN were applied as coatings on this fiber. Optical, scanning electron, and transmission electron microscopy were used to characterize the microstructure of the coatings and fibers. The effects of coating and high temperature exposure on the fiber strength were investigated using two-parameter Weibull distribution. TEM examination showed that the BN coating has a turbostratic structure, with the basal planes lying predominantly parallel to the fiber surface. Such an orientation of coating is desirable for easy crack deflection and subsequent fiber pullout in a composite. The BN coated Nextel 480 fiber showed that Weibull mean strength increased first and then decreased with increasing coating thickness. This was due to the surface flaw healing effect of the coating (up to 0.3 μm) while in the case of thick BN coating (1 μm), the soft nature of the coating material had a more dominant effect and resulted in a decrease of the fiber strength. High temperature exposure of Nextel 480 resulted in grain growth, which led to a strength loss.     

Structural characterization and catalytic activity of Pt dendrimer encapsulated nanoparticles supported over Al2O3 for SCR of NOx

Pt/Al2O3 and Pt-Mg/Al2O3 nano composites were successfully prepared by dendrimer templated synthesis route. The obtained dendritic nanoparticles were dispersed in alumina support and they were evaluated for SCR of NOx using methane as reductant. Thermal analysis results of uncalcined samples revealed that the oxygen can accelerate the rate of dendrimer shell decomposition. X-ray diffractograms of 500 degrees C calcined samples disclosed the amorphous nature of materials, whereas 1000 degrees C air calcined samples showed enhanced crystallinity as well as diffraction pattern corresponding to Pt and PtO. HRTEM images of Pt40-G4OH dendritic nanoparticles showed uniform particulate distribution with average particle size of 2.4 nm. The STEM results of 0.5 Pt/Al2O3 sample calcined at 500 degrees C exhibited a wide range of particles between 2 and 20 nm. This indicates the huge segregation of platinum metal particles during impregnation and subsequent calcination. Among the synthesized materials 0.5 wt% Pt/Al2O3 sample showed excellent conversion and selectivity for SCR of NOx.     

Thioflavin T‐Amyloid Hybrid Nanostructure for Biocatalytic Photosynthesis

Amyloidogenic peptides can self‐assemble into highly ordered nanostructures consisting of cross β‐sheet‐rich networks that exhibit unique physicochemical properties and high stability. Light‐harvesting amyloid nanofibrils are constructed by employing insulin as a building block and thioflavin T (ThT) as a amyloid‐specific photosensitizer. The ability of the self‐assembled amyloid scaffold to accommodate and align ThT in high density on its surface allows for efficient energy transfer from the chromophores to the catalytic units in a similar way to natural photosystems. Insulin nanofibrils significantly enhance the photoactivity of ThT by inhibiting nonradiative conformational relaxation around the central C? C bonds and narrowing the distance between ThT molecules that are bound to the β‐sheet‐rich amyloid structure. It is demonstrated that the ThT‐amyloid hybrid nanostructure is suitable for biocatalytic solar‐to‐chemical conversion by integrating the light‐harvesting amyloid module (for nicotinamide cofactor regeneration) with a redox biocatalytic module (for enzymatic reduction).     

Evaluation of multi-layered graphene surface plasmon resonance-based transmission type fiber optic sensor

Graphene is a zero band-gap semi-metal with remarkable electromagnetic and mechanical characteristics. This study is the first ever attempt to use graphene in the surface plasmon resonance (SPR) sensor as replacement material for gold/silver. Graphene, comprised of a single atomic layer of carbon, is a purely two-dimensional material and it is an ideal candidate for use as a biosensor because of its high surface-to-volume ratio. This sensor is based on the resonance occasion of the surface plasmon wave (SPW) according to the dielectric constants of each metal film and detected material in gas or aqueous phase. Graphene in the SPR sensor is expected to enlarge the range of analyte to bio-aerosols based on the superior electromagnetic properties of graphene. In this study, a SPR-based fiber optic sensor coated with multi-layered graphene is described. The multi-layered graphene film synthesized by chemical vapor deposition (CVD) on Ni substrate was transferred on the sensing region of an optical fiber. The graphene coated SPR sensor is used to analyze the interaction between structured DNA biotin and Streptavidin is analyzed. Transmitted light after passing through the sensing region is measured by a spectrometer and multimeter. As the light source, blue light which of 450 to 460 nm in wavelength was used. We observed the SPR phenomena in the sensor and show the contrary trends between bare fiber and graphene coated fiber. The fabricated graphene based fiber optic sensor shows excellent detection sensitivity of the interaction between structured DNA and Streptavidin.