Micropore-Boosted Layered Double Hydroxide Catalysts: EIS Analysis in Structure and Activity for Effective Oxygen Evolution Reactions

Since the oxygen evolution catalysis process is vital yet arduous in energy conversion and storage devices, it is highly desirous but extremely challenging to engineer earth-abundant, noble-metal-free nanomaterials with superior electrocatalytic activity toward effective oxygen evolution reactions (OERs). Herein, we construct a prismlike cobalt–iron layered double hydroxide (Co–Fe LDH) with a Co/Fe ratio of 3:1 utilizing a facile self-templated strategy. Instead of carbon-species-coupled treatment, we focus on ameliorating the intrinsic properties of LDHs as OER electrocatalysts accompanied by the hierarchical nanoflake shell, well-defined interior cavity, and numerous microporous defects. In contrary to conventional LDHs synthesized via a one-pot method, Co–Fe LDHs fabricated in this work possess a huge specific surface area up to 294.1 m2 g–1, which not only provides abundant active sites but also expedites the kinetics of the OER process. The as-prepared Co–Fe LDH electrocatalysts exhibit advanced electrocatalytic performance and a dramatic stability of the OER in an alkaline environment. In particular, the contribution of micropore defects is clearly discussed according to the electrochemical impedance spectroscopy analysis, in which the time constant of the OER at the micropore defect is several orders of magnitude smaller than that at the exterior of Co–Fe LDHs, forcefully verifying the intrinsic catalytic activity enhancement derived from the micropore defects. This work provides a promising model to improve OER electrocatalyst activity via produce defects and research the contribution of micropore defects

Supplemental Material, ESI - Peptide-coated palladium nanoparticle for highly sensitive bioanalysis of trypsin in human urine samples

Supplemental Material, ESI for Peptide-coated palladium nanoparticle for highly sensitive bioanalysis of trypsin in human urine samples by Guohua Zhou, Huimin Jiang, Yanfang Zhou, Peilian Liu, Yongmei Jia, and Cui Ye in Nanomaterials and Nanotechnology</p

Densities and Viscosities of the Ternary Mixtures of Decalin (1) + <i>n</i>‑Hexadecane (2) + 1‑Butanol (3) and Corresponding Binary Systems

Active cooling by endothermic hydrocarbon fuels (EHFs) is considered as a practical approach to deal with the thermal management problem of hypersonic aircrafts. As a typical component of EHFs, decalin is usually thermally stable while it is apt to coke and has poor combustion performance. n-Hexadecane, a normal alkane with a relatively high H/C ratio, can effectively improve the combustion performance of EHFs, and 1-butanol has remarkable anti-coking properties. As a fundamental work for fuel design, decalin, n-hexadecane, and 1-butanol were selected as model compounds to construct a surrogate fuel system, which was used to investigate the effects of composition and condition on its thermophysical properties. Densities (ρ) and viscosities (η) of the ternary system of decalin (1) + n-hexadecane (2) + 1-butanol (3) and corresponding binary systems were measured at temperatures T = (293.15 to 333.15) K and pressure p = 0.1 MPa. The excess molar volumes (VmE) and the viscosity deviations (Δη) of the mixtures were calculated and fitted to several semi-empirical equations. The tendencies of VmE and Δη with composition and temperature were discussed from intermolecular force and molecular size, respectively

Correlation between AcrB Trimer Association Affinity and Efflux Activity

The majority of membrane proteins function as oligomers. However, it remains largely unclear how the oligomer stability of protein complexes correlates with their function. Understanding the relationship between oligomer stability and activity is essential to protein research and to virtually all cellular processes that depend on the function of protein complexes. Proteins make lasting or transient interactions as they perform their functions. Obligate oligomeric proteins exist and function exclusively at a specific oligomeric state. Although oligomerization is clearly critical for such proteins to function, a direct correlation between oligomer affinity and biological activity has not yet been reported. Here, we used an obligate trimeric membrane transporter protein, AcrB, as a model to investigate the correlation between its relative trimer affinity and efflux activity. AcrB is a component of the major multidrug efflux system in Escherichia coli. We created six AcrB constructs with mutations at the transmembrane intersubunit interface, and we determined their activities using both a drug susceptibility assay and an ethidium bromide accumulation assay. The relative trimer affinities of these mutants in detergent micelles were obtained using blue native polyacrylamide gel electrophoresis. A correlation between the relative trimer affinity and substrate efflux activity was observed, in which a threshold trimer stability was required to maintain efflux activity. The trimer affinity of the wild-type protein was approximately 3 kcal/mol more stable than the threshold value. Once the threshold was reached, an additional increase of stability in the range observed had no observable effect on protein activity

Ligating Dopamine as Signal Trigger onto the Substrate via Metal-Catalyst-Free Click Chemistry for “Signal-On” Photoelectrochemical Sensing of Ultralow MicroRNA Levels

The efficiency of photon-to-electron conversion is extremely restricted by the electron–hole recombinant. Here, a new photoelectrochemical (PEC) sensing platform has been established based on the signal amplification of click chemistry (CC) via hybridization chain reaction (HCR) for highly sensitive microRNA (miRNA) assay. In this proposal, a preferred electron donor dopamine (DA) was first assembled with designed ligation probe (probe-N₃) via amidation reaction to achieve DA-coordinated signal probe (P_DA-N₃). The P_DA-N₃ served as a flexible trigger to signal amplification through efficiently suppressing the electron–hole recombinant. Specifically, the P_DA-N₃ can be successfully ligated into the trapped hairpins (H1 and H2) via the superior ligation method of metal-catalyst-free CC, in which the electron donor DA was introduced into the assay system. Moreover, the enzyme-free HCR, employed as a versatile amplification way, ensures that lots of P_DA-N₃ can be attached to the substrate. This PEC sensing for miRNA-141 detection illustrated the outstanding linear response to a concentration variation from 0.1 fM to 0.5 nM and a detection limit down to 27 aM, without additional electron donors. The sensor is further employed to monitor miRNA-141 from prostate carcinoma cell (22Rv1), showing good quantitative detection capability. This strategy exquisitely influences the analytical performance and offers a new PEC route to highly selective and sensitive detection of biological molecules

Self-Interconnected Porous Networks of NiCo Disulfide as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

Electrochemical splitting of water has been viewed as a highly efficient technique to produce clean hydrogen and oxygen energy. However, designing inexpensive multifunctional electrocatalysts with high performance is a great challenge. Here, a unique three-dimensional catalyst of self-interconnected porous Ni–Co disulfide networks grown on carbon cloth [(Ni0.33Co0.67)­S2 nanowires (NWs)/CC] was prepared by a facile hydrothermal method coupled with further low-temperature sulfuration strategy. As a bifunctional electrocatalyst, (Ni0.33Co0.67)­S2 NWs/CC exhibits a remarkable activity to catalyze both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). To drive a current density of 100 mA cm–2, (Ni0.33Co0.67)­S2 NWs/CC needs the overpotentials of 156 mV in 0.5 M H2SO4 solution and 334 mV in 1.0 M KOH solution for HER, respectively. Moreover, when used as a catalyst of OER, (Ni0.33Co0.67)­S2 NWs/CC needs an overpotential of 295 mV to produce a current density of 100 mA cm–2. The excellent electrochemical properties are mainly attributed to the synergetic catalysis of a Ni–Co-based bimetallic disulfide, the porous network structure, and the high conduction of CC. Moreover, the two-electrode alkaline water-splitting system constructed by (Ni0.33Co0.67)­S2 NWs/CC only needs a low cell voltage of 1.57 V to approach 10 mA cm–2. This work offers more new insights for the design and preparation of the non-noble metal catalysts based on transition metal sulfides with excellent electrocatalytic performance in overall water splitting

Self-Interconnected Porous Networks of NiCo Disulfide as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

Electrochemical splitting of water has been viewed as a highly efficient technique to produce clean hydrogen and oxygen energy. However, designing inexpensive multifunctional electrocatalysts with high performance is a great challenge. Here, a unique three-dimensional catalyst of self-interconnected porous Ni–Co disulfide networks grown on carbon cloth [(Ni0.33Co0.67)­S2 nanowires (NWs)/CC] was prepared by a facile hydrothermal method coupled with further low-temperature sulfuration strategy. As a bifunctional electrocatalyst, (Ni0.33Co0.67)­S2 NWs/CC exhibits a remarkable activity to catalyze both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). To drive a current density of 100 mA cm–2, (Ni0.33Co0.67)­S2 NWs/CC needs the overpotentials of 156 mV in 0.5 M H2SO4 solution and 334 mV in 1.0 M KOH solution for HER, respectively. Moreover, when used as a catalyst of OER, (Ni0.33Co0.67)­S2 NWs/CC needs an overpotential of 295 mV to produce a current density of 100 mA cm–2. The excellent electrochemical properties are mainly attributed to the synergetic catalysis of a Ni–Co-based bimetallic disulfide, the porous network structure, and the high conduction of CC. Moreover, the two-electrode alkaline water-splitting system constructed by (Ni0.33Co0.67)­S2 NWs/CC only needs a low cell voltage of 1.57 V to approach 10 mA cm–2. This work offers more new insights for the design and preparation of the non-noble metal catalysts based on transition metal sulfides with excellent electrocatalytic performance in overall water splitting