Nanozyme catalysis-powered portable mini-drainage device enables real-time and universal weighing analysis of silver ions and silver nanoparticles

Novel ultrasensitive Raman assay method based on enzyme mimetics for ultra trace of H2O2

Enzyme mimetics have been widely applied on H₂O₂ assay, but it is still challenging and interesting to realize the sensitive detection for ultra-trace H₂O₂. Here, an ultrasensitive Raman assay method based on novel WO₃@IP6-Fe³⁺ enzyme mimetics with peroxidase-like activity was established. WO₃ microspheres (MSs) were found to have weak peroxidase-like activity, and the combination of IP6-Fe³⁺ and WO₃ can produce stronger activity. WO₃@IP6-Fe³⁺ MSs showed polyhedron-like structure, uniform size, and smooth surface. Although WO₃@IP6-Fe³⁺ enzyme mimetics have low catalytic efficiency and high absorbance background, the proposed Raman method can bypass the above problems. In Raman method, high concentration of WO₃@IP6-Fe³⁺ can be used to overcome low catalytic efficiency without high absorbance background. Moreover, 3,3',5,5'-tetramethylbenzidine oxide has prominent characteristic Raman peak at 1608 cm^-1, greatly improving the sensitivity and eliminating interference of impurities. Due to the high sensitivity and low background, Raman assay showed the ultra-low limit of detection (5.49 × 10^-15 M), which was 4-7 orders of magnitude lower than other detection methods. The ultrasensitive Raman assay not only provided the possibility for the enzyme mimetics-based detection of ultra-trace H₂O₂, but also enable the enzyme mimetics with low activity to be applied.

Catalytically active silver nanoparticles stabilized on a thiol-functionalized metal-organic framework for an efficient hydrogen evolution reaction

A post-synthetic technique, Solvent Assisted Ligand Incorporation (SALI), was used for thiol functionalization in the zirconium-based metal-organic framework NU-1000. This thiol-functionalized MOF was employed as a support for the growth of silver nanoparticles (Ag NPs) through coordination of a Ag(I) complex with a node-anchored thiol-ligand, followed by the reduction of Ag(I) to Ag(0). X-ray photoelectron spectroscopy revealed that the ratio of Ag(0) to Ag(I) proportionally increased with the loading of silver ions. The HER activity increased with the enhancement of Ag(0) in the system and the best efficiency was observed for the composite with ∼95% Ag(0). This composite displayed an overpotential of 165 mV in an acidic medium at 10 mA cm^-2 and a Tafel slope of 53 mA dec^-1. The loading of silver beyond the optimum value led to the aggregation of the particles which affected the overpotential substantially. The catalyst demonstrated appreciable static stability for 24 h, which promotes the use of the material as an HER catalyst. Therefore, these results emphasized that Ag NPs embedded onto a thiol-functionalized MOF is a propitious material for developing a clean and renewable energy source.

Lighting Up Agricultural Sustainability in the New Era through Nanozymology: An Overview of Classifications and Their Agricultural Applications

With the concept of sustainable agriculture receiving increasing attention from humankind, nanozymes, nanomaterials with enzyme-like activity but higher environmental endurance and longer-term stability than natural enzymes, have enabled agricultural technologies to be reformative, economic, and portable. Benefiting from their multiple catalytic activities and renewable nanocharacteristics, nanozymes can shine in agricultural scenarios using enzyme engineering and nanoscience, acting as sustainable toolboxes to improve agricultural production and reduce the risk to agricultural systems. Herein, we comprehensively discuss the classifications of nanozymes applied in current agriculture, including peroxidase-like, oxidase-like, catalase-like, superoxide dismutase-like, and laccase-like nanozymes, as well as their biocatalytic mechanisms. Especially, different applications of nanozymes in agriculture are deeply reviewed, covering crop protection and nutrition, agroenvironmental remediation and monitoring, and agroproduct quality monitoring. Finally, the challenges faced by nanozymes in agricultural applications are proposed, and we expect that our review can further enhance agricultural sustainability through nanozymology.

How molecular interactions tune the characteristic time of nanocomposite colloidal sensors

HYPOTHESIS

Mass transport critically controls the performance of colloidal metal-polymer sensors. We hypothesize that molecular-level pair interactions, such as electric, steric, and specific binding effects, govern the mass transport and, in return, the characteristic time of these sensors.

THEORY

Here we present a simple theory guided by experimental data to examine the sensing performance of two usually encountered archetypal metal-polymer sensors, namely (1) core-shell and (2) yolk-shell architectures. For this purpose, we use the static reactive density functional theory framework, determining how (i) charge, (ii) size, and (iii) non-covalent binding factors modulate the characteristic time.

FINDINGS

We show how an interplay between diffusivity and partitioning governs the sensing time of the sensors, where an anti-correlation cancellation between them renders the time non-trivial. Our study demonstrates that the convoluted substrate-hydrogel shell interaction controls the characteristic time of these colloidal sensors, especially when the sensors are in a collapsed state. Notably, the substrates with a high dipole moment tend to equilibrate greatly, but undesirably, at the shell-solution interface. With this, we encourage the formation of a metastable sorption state.