Constructing built-in electric field in oxygen vacancies-enriched Fe3O4-FeSe2 heterojunctions supported on reduced graphene oxide for efficient overall water splitting.

Combining interfacial oxygen vacancy engineering with a built-in electric field (BEF) technique is an efficient way to build efficient and practical electrocatalytic water-splitting catalysts. In this study, a Fe3O4-FeSe2 heterojunction catalyst with oxygen vacancies supported on reduced graphene oxide (rGO) was designed and successfully fabricated using a simple two-step hydrothermal method. Owing to the different Fermi levels of Fe3O4 and FeSe2, a BEF was generated at the interface, which enhanced the separation of negative and positive charges, thus optimizing the adsorption of hydrogen/oxygen intermediates on the heterostructures and improving the activity of the catalyst. Experimental results show that Fe3O4-FeSe2/rGO/NF exhibits excellent hydrogen and oxygen evolution performances, with low overpotentials of 234/300 mV at 100 mA⋅cm-2. A water electrolyzer assembled with Fe3O4-FeSe2/rGO/NF as both the anode and cathode requires only a small potential of 1.78 V to reach a current density of 100 mA⋅cm-1. This study provides an innovative approach for constructing a catalyst with excellent electrocatalytic performance for overall water splitting.

In Situ Construction of NiCoMn-LDH Derived from Zeolitic Imidazolate Framework on Eggshell-Like Carbon Skeleton for High-Performance Flexible Supercapacitors.

Active compounds based on LDH (ternary layered double hydroxide) are considered the perfect supercapacitor electrode materials on account of their superior electrochemical qualities and distinct structural characteristics, and flexible supercapacitors are an ideal option as an energy source for wearable electronics. However, the prevalent aggregation effect of LDH materials results in significantly compromised actual specific capacitance, which limits its broad practical applications. In this research, a 3D eggshell-like interconnected porous carbon (IPC) framework with confinement and isolation capability is designed and synthesized by using glucose as the carbon source to disperse the LDH active material and enhance the conductivity of the composite material. Second, by constructing NiCoMn-LDH nanocage structure based on ZIF-67 (zeolitic imidazolate framework-67) at the nanometer scale the obtained IPC/NiCoMn-LDH electrode material can expose more active sites, which allows to achieve excellent specific capacitance (2236 F g-1/ 310.6 mAh g-1 at 1 A g-1), good rate as well as the desired cycle stability (85.9% of the initial capacitance upon 5000 cycles test). The constructed IPC/NiCoMn-LDH//IPC ASC (asymmetric supercapacitor) exhibits superior capacitive property (135 F g-1/60.1 mAh g-1 at 0.5 A g-1) as well as desired energy density (40 Wh kg-1 at 800 W kg-1).

Time-gated luminescence probe for ratiometric and luminescence lifetime detection of Hypochorous acid in lysosomes of live cells.

Time-gated luminescence (TGL) probes based on lanthanide complexes have appealed wide attention in the detection of biologically relevant analytes because of their inimitable photophysical properties. In this work, a TGL probe (TR-HOCl) based on intramolecular Förster resonance energy transfer (FRET) system for specific determination of hypochlorous acid (HOCl) was designed and synthesized, in which a rhodamine derivative (energy acceptor) was conjugated to a luminescent Tb3+ complex (energy donor). After reacting with HOCl, the Tb3+ emission of TR-HOCl at 540 nm declined while the rhodamine emission at 580 nm increased, which leaded to an increase of the TGL intensity ratio of rhodamine to Tb3+ complex (I560/I540) up to ~9-fold. The dose-dependent increase of I560/I540 gives a nice linearity in HOCl concentration range of 0.5-45 µM. The detection limit of for HOCl was determined to be 0.34 µM. Interestingly, the average luminescence lifetime of the Tb3+ emission decreased (from 588 µs to 254 µs) accompanied with the FRET process and the value gave a fine linearity to the variation of HOCl concentration. Additionally, TR-HOCl showed great selectivity for recognition of HOCl over other ROS, RNS, biothiols and other interference. These properties endow TR-HOCl to be conveniently applied for high accurate recognition of HOCl with ratiometric TGL and luminescence lifetime dual-signal output. Finally, TR-HOCl was successfully applied for the TGL determination of HOCl in HepG2 cells. The co-localization experiments of TR-HOCl with LysoSensor Green revealed the lysosome-localizing property of the probe in live cells. The study demonstrated that TR-HOCl could be a competent tool for investigating roles of HOCl in various physiological processes.

Suppressed blinking behavior of CdSe/CdS QDs by polymer coating.

Semiconductor quantum dots (QDs) are very important fluorescent nanocrystals with excellent optical properties. However, QDs, at the single-particle level, show severe fluorescence intermittency (or blinking) on a wide time scale from milliseconds to minutes, which limits certain optical and biological applications. Generally, blinking behavior of QDs strongly depends on their surface state and surrounding environment. Therefore, current blinking suppression approaches are mostly focused on the introduction of an inorganic shell and organic small molecule compounds. In this study, we described a "bottom up" approach for the synthesis of CdSe/CdS/polymer core/shell/shell QDs via the in situ one-pot polymerization approach in order to control the blinking behavior of QDs. Three monomers (dithiothreitol (DTT), phenylenediamine (PDA), and hexamethylenediamine (HDA)) were respectively used to polymerize with hexachlorocyclotriphosphazene (HCCP), and then the polyphosphazene polymers were obtained with cyclotriphosphazene as the basic macromolecular backbone. By regulating the molar ratios of the activated comonomers, we can control the blinking behavior of CdSe/CdS/polymer QDs. Under the optimal conditions, the percentage of "non-blinking" CdSe/CdS/polymer QDs (the "on time" fraction > 99% of the overall observation time) was up to 78%. The suppression mechanism was attributed to the efficient passivation of QD surface traps by the sulfhydryl or phenyl groups in the polyphosphazene polymers.

Efficient oxygen reduction catalysts formed of cobalt phosphide nanoparticle decorated heteroatom-doped mesoporous carbon nanotubes.

Oxygen reduction catalysts based on heteroatom-doped mesoporous carbon nanotubes loaded with Co2P nanoparticles were skilfully fabricated. The electronic interaction between the embedded Co2P nanoparticles and the heteroatom-doped carbon structures could strongly promote the ORR catalytic performance of the heteroatom-doped carbon nanotubes.

Enhancement of the electrocapacitive performance of manganese dioxide by introducing a microporous carbon spheres network.

An amorphous MnO(2)·nH(2)O/microporous carbon spheres (α-MnO(2)·nH(2)O/MCS) composite electrode material is prepared by a chemical co-precipitation method. It is observed that the amorphous MnO(2) particles are deposited on the surface of the MCS, which form a network with a uniquely developed three-dimensional open porous system containing macropores, mesopores and micropores. The electrochemical measurements reveal that the composite electrode material presents a much more stable and reversible capacitance behavior compared to the pure α-MnO(2)·nH(2)O in 1 M of Na(2)SO(4) electrolyte. The composite containing 25 wt% MCS exhibits optimal specific capacitance of 218.2 F g(-1) at 2 mV s(-1), and is still as high as 112.4 F g(-1) at 100 mV s(-1), while a drastic reduction from 197.0 F g(-1) at 2 mV s(-1) to only 40.7 F g(-1) at 100 mV s(-1) occurs for the pure α-MnO(2)·nH(2)O. The composite also shows a rather high electrode-specific capacitance of 3.13 F cm(-2) and a long cycle life. The remarkable enhancement in the electrochemical performance is mainly attributed to the microporous structure of the MCS contributing to the deposition of MnO(2) particles on the surface of the MCS, and the uniquely developed porous network of the composite facilitating the rapid transport of the electrolyte. These factors result in the high electrochemical utilization of MnO(2), a great reduction of the equivalent series resistance, and hence the relatively high and stable electrochemical behavior.