Nitric oxide (NO) has been implicated in a variety of physiological and pathological processes. Monitoring cellular levels of NO requires a sensor to feature adequate sensitivity, transient recording ability and biocompatibility. Herein we report a single-atom catalysts (SACs)-based electrochemical sensor for the detection of NO in live cellular environment. The system employs nickel single atoms anchored on N-doped hollow carbon spheres (Ni SACs/N-C) that act as an excellent catalyst for electrochemical oxidation of NO. Notably, Ni SACs/N-C shows superior electrocatalytic performance to the commonly used Ni based nanomaterials, attributing from the greatly reduced Gibbs free energy that are required for Ni SACs/N-C in activating NO oxidation. Moreover, Ni SACs-based flexible and stretchable sensor shows high biocompatibility and low nanomolar sensitivity, enabling the real-time monitoring of NO release from cells upon drug and stretch stimulation. Our results demonstrate a promising means of using SACs for electrochemical sensing applications.

In this study, we present a three-in-one catalytic platform for intrinsic oxidase-, peroxidase-, and catalase-like activity, which is enabled by epitaxial growth of the MoS nanosponge on 2D Co(OH) nanoflakes [2D Co(OH) NFs] (CoMo hybrids). First, the 2D Co(OH) NFs are stripped from hierarchical three-dimensional Co(OH) nanoflowers which are synthesized in an eco-friendly way via one-step surfactant-free chemical route. Next, the porous MoS nanosponge is decorated on the 2D Co(OH) NFs' surface using a solvothermal process forming heterogeneous nanostructured CoMo hybrids. Finally, because of the host-guest interaction, that is, after the epitaxial growth of spongy MoS on 2D Co(OH) NFs, the heterogeneous nanostructure of CoMo hybrids exhibits unpredictable triple-enzyme mimetic activity simultaneously. The mechanisms of the oxidase-like properties are investigated by density functional theory (DFT) calculations, and it is discovered that a simple reaction/dissociation of O absorbed on Co-Mo thin films can explain the enhanced oxidase-like activity of the CoMo hybrids. In addition, the CoMo hybrids are also reproducible, stable, and reusable, that is, after 10 cycle uses, >90% mimic enzyme activity of the CoMo hybrids is still maintained. The oxidase-like activity of the CoMo hybrids enables it to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) producing the blue oxTMB, which can selectively oxidize ascorbic acid (AA) and pave a new avenue for colorimetric sensing of AA. The proposed colorimetric strategy has been successfully utilized to measure AA in rat brain during the cerebral calm/ischemia process. Our findings provide in-depth insight into the future research of enzyme-like activities and might help to elucidate the mechanism and understand the role of epitaxial growth on the properties and application of hybrid nanostructures.

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The oxygen reduction reaction (ORR) is of great importance for various renewable energy conversion technologies such as fuel cells and metal-air batteries. Heteroatom-doped carbon nanomaterials have proven to be robust metal-free electrocatalysts for ORR in the above-mentioned energy devices. Herein, we demonstrate the synthesis of novel highly porous N-doped carbon nanoplatelets (N-HPCNPs) derived from oatmeal (or a biological material) and we show the materials’ high-efficiency as electrocatalyst for ORR. The obtained N-HPCNPs hybrid materials exhibit superior electrocatalytic activities towards ORR, besides excellent stability and good methanol tolerance in both basic and acidic electrolytes. The unique nanoarchitectures with rich micropores and mesopores, as well as the high surface area-to-volume ratios, present in the materials significantly increase the density of accessible catalytically active sites in them and facilitate the transport of electrons and electrolyte within the materials. Consequently, the N-HPCNPs catalysts hold a great potential to serve as low-cost and highly efficient cathode materials in direct methanol fuel cells (DMFCs).

In this work, one-dimensional core–shell Cu@Ni nanorods which were anchored on two dimensional reduced graphene oxide (rGO) heterostructures were successfully prepared by a simple co-reduction method.