RESUMEN

Two-dimensional layered membranes with high and stable ion transport properties have various applications in nanofluidic devices; however, their construction remains a considerable challenge. Herein, we develop a superstable aramid nanofiber/graphite composite membrane with numerous one-dimensional and two-dimensional nano-confined interspaces for ultrafast ion transport. The fabricated flexible and scalable membrane exhibits high tensile strength (∼115.3 MPa) even after immersion in water for 90 days. Further, the aramid nanofiber/graphite conductor features the surface-charge-governed ion transport behavior. The ionic conductivity of the membrane at a low potassium chloride concentration of 10-4 mol/L can be enhanced by 16 times that of the bulk counterpart. More importantly, its structure and ionic conductivity remain unchanged even after immersion in different harsh solutions (e.g., acid, base, and ethanol) for over 30 days. Molecular dynamics simulations reveal that the superstability of the membrane is attributable to the robust interchain interactions within the aramid nanofibers and the strong interfacial interactions between the aramid nanofibers and graphite nanosheets. This study highlights the superior structural stability of the proposed flexible and scalable aramid nanofiber/graphite composite membrane, which could be employed in advanced nanofluidic devices for application under extreme working environments.

RESUMEN

A spline-in-compression method, implicit in nature, for computing numerical solution of second order nonlinear initial-value problems (IVPs) on a mesh not necessarily equidistant is discussed. The proposed estimation has been derived directly from consistency condition which is third-order accurate. For scientific computation, we use monotonically descending step lengths. The suggested method is applicable to a wider range of physical problems including the problems which are singular in nature. This is possible due to off-step discretization employed in the spline technique. We examine the absolute stability and super-stability of the method when applied to a problem of physical significances. We have shown that the method is absolutely stable in the case of graded mesh and super stable in the case of constant mesh. The advantage of our method lies in it being highly cost and time effective, as we employ a three-point compact stencil, thereby reducing the algebraic calculations considerably. The proposed method which is applicable to singular, boundary layer and singularly perturbed problems is a research gap which we overcame by proposing this new compact spline method.

RESUMEN

Transition metal nitrides have shown large potential in industrial application for realization of the high active and large current density toward overall water splitting, a strategy to synthesize an inexpensive electrocatalyst consisting of Ni nanoparticles embedded metallic MoN microrods cultured on roughened nickel sheet (Ni/MoN/rNS) through underfocus laser heating on NiMoO4 ·xH2 O under NH3 atmosphere is posited. The proposed laser preparation mechanism of infocus and underfocus modes confirms that the laser induced stress and local high temperature controllably and rapidly prepared the patterned Ni/MoN/rNS electrodes in large size. The designed Ni/MoN/rNS presents outstanding catalytic performance for hydrogen evolution reaction (HER) with a low overpotential of 67 mV to deliver a current density of 10 mA cm-2 and for the oxygen evolution reaction (OER) with a small overpotential of 533 mV to deliver 200 mA cm-2 . Density functional theory (DFT) calculations and Kelvin probe force microscopy (KPFM) further verify that the constructed interface of Ni/MoN with small hydrogen absorption Gibbs free energy (ΔGH* ) (-0.19 eV) and similar electrical conductivity between Ni and metallic MoN, which can explain the high intrinsic catalytic activity of Ni/MoN. Further, the constructed two-electrode system (-) Ni/MoN/rNS||Ni/MoN/rNS (+) is employed in an industrial water-splitting electrolyzer (460 mA cm-2 for 120 h), being superior to the performance of commercial nickel electrode.

RESUMEN

Metal organic gels (MOGs) as a new type of porous soft-hybrid supramolecular material have attracted widespread interest in various aspects due to their unique optical properties. In this work, we report a novel electrochemiluminescence (ECL) emission (679 nm) lanthanide MOG, which has been synthesized by a simple and rapid method at room temperature. This MOG (Tb-Ru-MOG) consists of a central metal ion, terbium (III), and two different ligands, tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium (II) dichloride (Ru(dcbpy)32+) and 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine (Hcptpy). Compared with the classic system of tris(2,2'-bipyridyl) ruthenium (II) dichloride (Ru(bpy)32+)/S2O82-, Tb-Ru-MOG/S2O82- owns a narrower potential sweep range (0.00 to -0.85 V) and a more stable and stronger ECL signal. Interestingly, the ECL intensity only decreased 2.0 and 0.1% after continuous scanning for 8000 s and storing at room temperature for 3 months. The possible ECL mechanism has been discussed in detail, which is mainly attributed to the internal synergies (antenna effect and energy transfer) and external co-reactant. Inspired by the unique luminescence characteristics of Tb-Ru-MOG, the application in electroanalytical chemistry was identified by the ECL on-off response for epinephrine with a linear range from 1.0 × 10-10 to 1.0 × 10-3 mol·L-1 and a detection limit of 5.2 × 10-11 mol·L-1. The results suggest that the as-proposed Tb-Ru-MOG will provide a robust pathway for new ECL luminophores in analysis.

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RESUMEN

As practical interest in stretchable electronics increases for future applications in wearables, healthcare, and robotics, the demand for electrical interconnects with high electrical conductivity, durability, printability, and adhesion is growing. Despite the high electrical conductivity and stretchability of most previous interconnects, they lack stable conductivity against strain and adhesion to stretchable substrates, leading to a limitation for their practical applications. Herein, we propose a stretchable conductive adhesive consisting of silver particles with carbon nanotube as an auxiliary filler in silicone adhesives. The conductive adhesive exhibits a high initial conductivity of 6450 S cm-1. They show little change in conductivity over 3000 stretching cycles at 50% strain, currently the highest stability reported for elastic conductors. Based on strong adhesion to stretchable substrates, the gel-free, dry adhesives printed on an elastic bandage for electrocardiography monitoring exhibit an extremely stable performance upon movement of the subject, even after several cycles of detachment-reattachment and machine washing.

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