The NiCo/NiO–CoOx ultra-thin layered catalyst exhibits high-performance towards H2 generation from N2H4·H2O without alkali as a catalyst promoter at 25 °C.

The volume-dependent rotational diffusion coefficient of gold nanorod was used to monitor the formation of protein corona in homogeneous solution in real time. The detection of particle thickness change could reach subnanometer sensitivity.

Liquid−liquid phase separation (LLPS) underlies the formation mechanism of membraneless biomolecular condensates locally to perform important physiological functions such as selective autophagy, but little is known about the relationship between their dynamic structural organization and biophysical properties. Here, a dark-field microscopy based single plasmonic nanoparticle tracking (DFSPT) technique was introduced to simultaneously monitor the diffusion dynamics of multiple gold nanorod (AuNR) probes in a protein LLPS system and to quantitatively characterize the spatiotemporal heterogeneity of the LLPS condensates during their phase transformation. Based on spatially and temporally resolved analysis of the diffusional behavior of the AuNRs, structure and material properties of p62 condensates, such as the viscoelasticity, the compartmentalization, and the recruitment of protein-covered nanoparticles into the large droplet, have been observed. Moreover, the nonsmooth droplet interface, its solidification after further phase transition or maturation, and the size effect of the inner vacuoles have also been revealed. Our method can be potentially applied to in vitro investigation of different reconstituted membrane-free biomolecular condensates and in vivo study of their dynamic evolution.

A high‐speed darkfield microscope has been developed to monitor the rapid rotation of single gold nanorods (AuNRs) and used to study the spatiotemporal heterogeneity of chemical reactions in free solution. A wide range of viscosities from 237 cP to 0.8 cP could be detected conveniently. We studied H2O2 decomposition reactions that were catalyzed by AuNRs coated with Pt nanodots (AuNR@PtNDs) and observed two different rotational states. The two states and their transitions are related to the production and the amalgamation of O2 nanobubbles on the nanorod surface depending on H2O2 concentration. In addition, the local fluidic environment of pure water was found to be non‐uniform in time and space. This technique could be applied to study other chemical and biochemical reactions in solution.

Ah igh-speed darkfield microscope has been developed to monitor the rapid rotation of single gold nanorods (AuNRs) and used to study the spatiotemporal heterogeneity of chemical reactions in free solution. Awide range of viscosities from 237 cP to 0.8 cP could be detected conveniently.W e studied H 2 O 2 decomposition reactions that were catalyzedb y AuNRs coated with Pt nanodots (AuNR@PtNDs) and observed two different rotational states.T he two states and their transitions are related to the production and the amalgamation of O 2 nanobubbles on the nanorod surface depending on H 2 O 2 concentration. In addition, the local fluidic environment of pure water was found to be non-uniform in time and space.This technique could be applied to study other chemical and biochemical reactions in solution.The reaction mechanisms in nanoscopic systems often differ considerably in time and space due to their structural and dynamic heterogeneity, [1] so it is imperative to develop effective methods capable of following spatiotemporal changes directly at the single-particle level, [2] especially for nanoscale catalysts and self-propelled micro/nanomotors in complex fluidic surroundings.T oa void important intermediates and rare events being masked by ensemble-averaged measurements,p eople have established an umber of techniques that can monitor the activity and chemical states of single nanoparticles (NPs) under reaction conditions, [3] including single-molecule fluorescence imaging, [4] tipenhanced Raman spectroscopy, [5] surface plasmon resonance imaging, [6] and electrochemical methods. [7] Nevertheless,s o far these techniques have only been applied to nanoparticles immobilized on as olid substrate,w here the interfacial microenvironment and the information obtained on the reaction may not be the same as those in the homogeneous solution.Due to their high brightness and great photostability, plasmonic nanoparticles have been used recently as nonfluorescent single-particle optical probes. [8] With darkfield microscopy (DFM) or differential interference contrast microscopy,weand others have reported that the orientation and rotation of single AuNRs can be used to elucidate the dynamic processes of chromatographic desorption, endocy-tosis,a nd intracellular traffic of NPs. [9] However,d ue to the sampling rate of the cameras in these studies,only the nearly stationary AuNRs or slowly rotating AuNRs in high-viscosity environments have been monitored. Here,w er eport highspeed laser darkfield microscopy (HSLDFM) that is capable of sensing the transient rotational dynamics of single AuNRs in free solution at > 10 000 frames per second. With HSLDFM, we directly monitored the spatiotemporal variation of rotational diffusion of individual AuNR@PtNDs during the H 2 O 2 decomposition process,a nd observed behaviors related to the reaction dynamics of heterogeneous catalysis as well as the structure of water that were unexpected from ensemble measurements.Theo ptical measurement principle of HSLDFM (Figure 1a)issimilar to that previous...

Catalytic enzymes exhibiting enhanced motion have drawn extensive attention over the past decade; nevertheless, little is known about the effect on the environment induced by enzymes. Herein, we studied the active urease system by simultaneously monitoring the diffusion of single anisotropic gold nanorods (AuNRs) with high speed dark-field imaging. We found both the translational and the rotational diffusion coefficients of AuNRs were enhanced but with inconsistent degrees, indicating the catalytic reaction had a minor effect on the physiochemical properties of the environment according to the Stokes−Einstein equation. With the increase of substrate concentration, the diffusion of AuNRs showed increased spatial but decreased temporal heterogeneity. Additionally, high speed imaging revealed AuNRs could experience intermittent ballistic motion for tens of milliseconds. These results imply inhomogeneous distribution of enzymes in free solution induced by active enzymatic reactions.

Controlled assembly of nanoparticles (NPs) has garnered much interest over the past two decades. Beyond established techniques, new methods utilizing local short-range or large-scale long-range interactions remain to be explored to achieve diverse micro- and nanoscale structures. Here, we report the controlled emergence of vortex-pair arrays within monodispersed gold nanorods (AuNRs) by applying a direct current (dc) electric field across a pair of sawtooth electrodes. By employing in situ darkfield microscopy and particle collective analysis, we elucidate the mechanism behind the formation and stabilization of the NP vortices, attributing it to the combined effects of the electrode shape, high NP density, and high solution viscosity. We further explored the controllability of the vortex-pair arrays and obtained multiple complex vortices patterns. Our findings will facilitate the investigation of efficient and controlled dynamic assembly of NPs under external fields and help manufacture next-generation optoelectronic functional materials.

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