Pyro-photocatalytic Coupled Effect in Ferroelectric Bi0.5Na0.5TiO3 Nanoparticles for Enhanced Dye Degradation.

Advanced oxidation processes (AOPs), achieved through the continuous attack of reactive oxygen species (ROS), are considered the most efficient way to mineralize organic pollutants. Among them, photocatalysis is the most environmentally friendly strategy for pollution mitigation but is hampered by low conversion efficiency. By exploiting the coupling effect without changing the properties of the semiconductor, the application of pyroelectric fields can significantly improve the catalytic performance. The degradation rate of rhodamine B by Bi0.5Na0.5TiO3 (BNT) nanoparticles under temperature fluctuations and visible light irradiation was up to 98%. The performance was enhanced by 216.54% and 31.48% compared to the pyroelectric catalysis and photocatalysis alone, respectively. The improved performance is due to the introduced pyroelectric potential with the imposition of temperature fluctuations, which can make the domains enhance the polarization of ferroelectrics, thus promoting the charge separation. This method can significantly advance the coupled pyro-photocatalytic reaction of ferroelectric semiconductors and also can enable the synergistic utilization of multiple energy sources such as solar and thermal energy, which is a promising strategy for environmental remediation.

Differences and Similarities of Photocatalysis and Electrocatalysis in Two-Dimensional Nanomaterials: Strategies, Traps, Applications and Challenges.

Photocatalysis and electrocatalysis have been essential parts of electrochemical processes for over half a century. Recent progress in the controllable synthesis of 2D nanomaterials has exhibited enhanced catalytic performance compared to bulk materials. This has led to significant interest in the exploitation of 2D nanomaterials for catalysis. There have been a variety of excellent reviews on 2D nanomaterials for catalysis, but related issues of differences and similarities between photocatalysis and electrocatalysis in 2D nanomaterials are still vacant. Here, we provide a comprehensive overview on the differences and similarities of photocatalysis and electrocatalysis in the latest 2D nanomaterials. Strategies and traps for performance enhancement of 2D nanocatalysts are highlighted, which point out the differences and similarities of series issues for photocatalysis and electrocatalysis. In addition, 2D nanocatalysts and their catalytic applications are discussed. Finally, opportunities, challenges and development directions for 2D nanocatalysts are described. The intention of this review is to inspire and direct interest in this research realm for the creation of future 2D nanomaterials for photocatalysis and electrocatalysis.

Nanoconfined Electrochemical Sensing of Single Silver Nanoparticles with a Wireless Nanopore Electrode.

Single entity electrochemistry (SEE) has emerged as a promising method for precise measurement and fundamental understanding of the heterogeneity of single entities. Herein, we propose the dual responsive SEE sensing of the silver nanoparticles (AgNPs) collisions through a wireless nanopore electrode (WNE). Given the high temporal resolution and low background noise features, the Faradaic and capacitive currents provide the AgNPs' collision response. The electron transfer between the AgNPs and the electrode surface is identified under a bipolar electrochemical mechanism. Compared to the ultramicroelectrode, multistep oxidation of 30 nm AgNPs is observed due to the decreased interaction of the nanoparticles to the electrode. Moreover, the nanoconfinement of WNE plays a vital role in the repeated capturing of nanoparticles from the nontunneling region into the tunneling region until a complete oxidation. As a comparison, the collision of 5 nm AgNPs with higher interaction at the electrode surface shows great decrease in the multistep events. Thus, we propose a nanoconfined interaction based SEE method which could be used for simultaneously capturing the Faradaic and capacitive response. The nanoconfined interaction based SEE method holds great promise in the better understanding of heterogeneity of single particles.

Wireless nanopore electrodes for analysis of single entities.

Measurements of a single entity underpin knowledge of the heterogeneity and stochastics in the behavior of molecules, nanoparticles, and cells. Electrochemistry provides a direct and fast method to analyze single entities as it probes electron/charge-transfer processes. However, a highly reproducible electrochemical-sensing nanointerface is often hard to fabricate because of a lack of control of the fabrication processes at the nanoscale. In comparison with conventional micro/nanoelectrodes with a metal wire inside, we present a general and easily implemented protocol that describes how to fabricate and use a wireless nanopore electrode (WNE). Nanoscale metal deposition occurs at the tip of the nanopipette, providing an electroactive sensing interface. The WNEs utilize a dynamic ionic flow instead of a metal wire to sense the interfacial redox process. WNEs provide a highly controllable interface with a 30- to 200-nm diameter. This protocol presents the construction and characterization of two types of WNEs-the open-type WNE and closed-type WNE-which can be used to achieve reproducible electrochemical measurements of single entities. Combined with the related signal amplification mechanisms, we also describe how WNEs can be used to detect single redox molecules/ions, analyze the metabolism of single cells, and discriminate single nanoparticles in a mixture. This protocol is broadly applicable to studies of living cells, nanomaterials, and sensors at the single-entity level. The total time required to complete the protocol is ~10-18 h. Each WNE costs ~$1-$3.

Single molecule sensing of amyloid-ß aggregation by confined glass nanopores.

We have developed a glass nanopore based single molecule tool to investigate the dynamic oligomerization and aggregation process of Aß1-42 peptides. The intrinsic differences in the molecular size and surface charge of amyloid aggregated states could be distinguished through single molecule induced characteristic current fluctuation. More importantly, our results reveal that the neurotoxic Aß1-42 oligomer tends to adsorb onto the solid surface of nanopores, which may explain its instability and highly neurotoxic features.