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.

This study describes a facile and effective route to synthesize hybrid material consisting of Co₃O₄ nanoparticles anchored on nitrogen-doped reduced graphene oxide (Co₃O₄/N-rGO) as a high-performance tri-functional catalyst for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and H₂O₂ sensing. Electrocatalytic activity of Co₃O₄/N-rGO to hydrogen peroxide reduction was tested by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. Under a reduction potential at −0.6 V to H₂O₂, this constructing H₂O₂ sensor exhibits a linear response ranging from 0.2 to 17.5 mM with a detection limit to be 0.1 mM. Although Co₃O₄/rGO or nitrogen-doped reduced graphene oxide (N-rGO) alone has little catalytic activity, the Co₃O₄/N-rGO exhibits high ORR activity. The Co₃O₄/N-rGO hybrid demonstrates satisfied catalytic activity with ORR peak potential to be −0.26 V (vs. Ag/AgCl) and the number of electron transfer number is 3.4, but superior stability to Pt/C in alkaline solutions. The same hybrid is also highly active for OER with the onset potential, current density and Tafel slope to be better than Pt/C. The unusual catalytic activity of Co₃O₄/N-rGO for hydrogen peroxide reduction, ORR and OER may be ascribed to synergetic chemical coupling effects between Co₃O₄, nitrogen and graphene.

Recently, mesoporous silica nanoparticles (MSNs) have become popular nanomaterials in smart delivery systems. Although research progress in the application of MSNs as pesticide carriers has been achieved, multifunctional MSNs endowed with bright luminescent centers facilitating the tracking of MSNs in biological systems and versatile structural properties possessing a high drug loading capacity and regulable release are still highly desirable. In the present work, we reported a fluorophore-free method to endow MSNs with stable fluorescence and a double-shelled hollow structure; they were prepared by a selective-etching strategy and subsequent annealing treatment. The strong and stable luminescence is found to originate from the carbon dots generated from the calcination. Their well-defined morphological structure was confirmed by SEM and TEM imaging. These versatile silica nanoparticles served as a novel delivery system for the pesticide pyraclostrobin with a loading content of 28.5%. The pyraclostrobin-loaded nanoparticles showed an initial burst, followed by subsequent sustained release behavior. The fungicidal activity of pyraclostrobin-loaded silica nanoparticles against the fungus Phomopsis asparagi (Sacc.) as well as their visual observation in the mycelium was explored. Furthermore, the effect of pyraclostrobin-loaded nanoparticles on the morphology and ultrastructure of the mycelium was investigated by SEM and TEM observations. This research seeks to develop a novel nanocarrier platform for the potential application of pesticides in sustainable plant protection.

AMoS_x/Co(OH)₂ nanosheets were synthesized by forming amorphous MoS_x on Co(OH)₂ nanosheets. The aMoS_x/Co(OH)₂ nanosheets demonstrate excellent OER catalytic activity with only 350 mV at 10 mA cm⁻². The incorporation of amorphous molybdenum sulfide enhances the hydrophilicity, favoring the availability of reactant, and induces electron transfer for enhancing the OER catalytic activity of Co(OH)₂.