Glass micropipettes, atomic force microscope tips and nanoneedles can be used to interrogate cells, but these devices either have conical geometries that can damage cells during penetration or are incapable of continuous fluid handling. Here, we report a carbon-nanotube-based endoscope for interrogating cells, transporting fluids and performing optical and electrochemical diagnostics at the single organelle level. The endoscope, which is made by placing a multiwalled carbon nanotube (length, 50-60 µm) at the tip of a glass pipette, can probe the intracellular environment with a spatial resolution of ∼100 nm and can also access organelles without disrupting the cell. When the nanotube is filled with magnetic nanoparticles, the endoscope can be remotely manoeuvered to transport nanoparticles and attolitre volumes of fluids to and from precise locations. Because they are mounted on conventional glass micropipettes, the endoscopes readily fit standard instruments, creating a broad range of opportunities for minimally invasive intracellular probing, drug delivery and single-cell surgery.

Electrocatalytic water-splitting, a combination of oxygen and hydrogen evolution reactions (OER and HER), is highly attractive in clean energy technologies, especially for high-purity hydrogen production, whereas developing stable, earth-abundant, bifunctional catalysts has continued to pose major challenges. Herein, a mesoporous NiFe-oxide nanocube (NiFe-NC) system is developed from a NiFe Prussian blue analog metal-organic framework as an efficient bifunctional catalyst for overall water-splitting. The NiFe-NCs with ∼200 nm side length have a Ni/Fe molar ratio of 3:2 and is a composite of NiO and α/γ-FeO. The NCs demonstrate overpotentials of 271 and 197 mV for OER and HER, respectively, in 1 M KOH at 10 mA cm, which outperform those of 339 and 347 mV for the spherical NiFe-oxide nanoparticles having a similar composition. The electrolyzer constructed using NiFe-NCs requires an impressive cell voltage of 1.67 V to deliver a current density of 10 mA cm. Along with a mesoporous structure with a broad pore size distribution, the NiFe-NCs demonstrate the qualities of a desired corrosion-resistant water-splitting catalyst with long-term stability. The exposure of active sites at the edges and vertices of the NCs was validated to play a crucial role in their overall catalytic performance.

Herein, we present an innovative approach for transforming commonly available cellulose paper into a flexible and catalytic current collector for overall water splitting. A solution processed soak-and-coat method of electroless plating was used to render a piece of paper conducting by conformably depositing metallic nickel nanoparticles, while still retaining the open macroporous framework. Proof-of-concept paper-electrodes are realized by modifying nickel-paper current collector with model electrocatalysts nickel-iron oxyhydroxide and nickel-molybdenum bimetallic alloy through electrodeposition route. The paper-electrodes demonstrate exceptional activities towards oxygen evolution reaction and hydrogen evolution reaction, requiring overpotentials of 240 and 32 mV at 50 and −10 mA cm−2, respectively, even as they endure extreme mechanical stress. The generality of this approach is demonstrated by fabricating similar electrodes on cotton fabric, which also show high activity. Finally, a two-electrode paper-electrolyzer is constructed which can split water with an efficiency of 98.01%, and exhibits robust stability for more than 200 h.

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