Characterization of polymer bulk heterojunction photocell with unmodified C70 prepared with halogen-free solvent for indoor light harvesting

Although photocells are commonly characterized under AM1.5G 100 mW cm⁻² (1 sun) illumination, their performance under low light illumination is also important, because photocells are frequently used for indoor applications. In this study, polymer photocells based on a bulk heterojunction composite consisting of a low energy gap polymer PTB7 and unmodified C₇₀ prepared with a halogen-free solvent 1,2,4-trimethylbenzene have been characterized under the illumination of 1 sun or below. A typical photocell with the power conversion efficiency (PCE) of 4% at 1 sun shows the PCE of approximately 7% at 10⁻³ sun, which seems to fit for some indoor applications such as a permanent power source for a wireless sensor node. The sublinear dependence of short-circuit photocurrent on light intensity as well as the increase of fill-factor under low light illumination yields the increased efficiency under low light illumination. An analysis employing a one-diode equivalent circuit model suggests that the increased parallel resistance as well as the decreased saturation current of the diode under low light illumination accounts for the latter feature. It is also pointed out that the parallel resistance and/or the saturation current under dark strongly influence the PCE of a photocell under low light illumination. In addition, the dependence of the device performance on the light intensity is found to be useful for analyzing the effects of the thermal treatment and the PFN interlayer at cathode.     

Thermally stable Ni MOF catalyzed MgH2 for hydrogen storage

The poor kinetics is the main issue hindering MgH₂ for practical hydrogen storage application. In this work, the tricarboxybenzene was used to construct the stable Ni MOF (Ni-BTC300) as the catalyst for MgH₂. The prepared MOFs maintained their chemical structure after 300 °C calcining and doped to MgH₂ by ball milling. The dispersed, uniformly bonded Ni atoms can improve the kinetics of the composites, which could desorb 5.14 wt% H₂ within 3 min at 300 °C. And the stable MOF structure leading to good cycle stability in both kinetics and capacity, with retention of 98.2% after 10 cycles.     

Activation of graphene aerogel with phosphoric acid for enhanced electrocapacitive performance

We present a facile and efficient route to introduce in-plane nanopores on the graphene sheets by activation of graphene aerogel (GA) with phosphoric acid (H₃PO₄). Results from N₂ adsorption and TEM images showed that H₃PO₄ activation created mesopores with pore size of 2–8 nm on the graphene sheets. With such nanopores on graphene sheets, the activated GA exhibits a specific capacitance of 204 F g⁻¹, enhanced rate capability (69% capacitance retention from 0.2 to 30 A g⁻¹), reduced equivalent series resistance (3.8 mΩ) and shortened time constant (0.73 s) when comparing with the hydrothermally-derived pristine GA and thermally annealed GA in the absent of H₃PO₄. The excellent capacitive properties demonstrate that introduction of nanopores on GA by H₃PO₄ activation not only provides large ion-accessible surface area for efficient charge storage, but also promotes the kinetics of electrolyte across the graphene two-dimensional planes.     

Hydrothermal synthesis of WO3 films on the TiO2 substrates and their photochromic properties

Tungsten oxide (WO₃) films have been prepared on the synthesized TiO₂ substrates from a sodium tungsten precursor via a hydrothermal method. X-ray diffraction, scanning electron microscopy and transmission electron microscopy analyses were used to investigate the effect of precursor concentrations on the structures and morphologies of the films. Ordered WO₃ films were successfully synthesized on the as-grown TiO₂ substrates. With the concentrations increasing from 0.001 M to 0.024 M, the morphologies of the films changed from multi-layer laminated structure to ladder-shaped lamellar structure finally columnar structure. The results also showed that with an increase in precursor concentration, the observed absorptions at 365 nm of the films increased until precursor concentration of 0.016 M, and then decreased with higher concentration. The film obtained with precursor concentration of 0.016 M on the TiO₂ substrate had the best photochromic properties.     

Energy trade efficiency and its determinants: A Malmquist index approach

This paper adopts the Malmquist index approach to investigate multi-product energy trade efficiency and its determinants from an empirical perspective. Using trade statistics of coal, oil and gas of 40 countries over the period of 1995 to 2008, we found that the efficiency of bilateral energy trade ranged between 0.26 and 0.35 when imperfect substitution between different energy products is taken into account. This measure is significantly lower than those obtained from traditional gravity models. It suggests that the ability of cross-product substitution affects trade efficiency improvement which results from regional market integration and related trade policy. The results provide useful insights on predicting the pattern of future energy trade and hence have important implications for relevant countries to prioritize product-specific trade policies.     

Resonance Assignments of Lowly Populated and Unstable Enzyme Intermediate Complex under Real-Time Conditions

Unstable and low-abundance protein complexes represent a large family of transient protein complexes that are difficult to characterize, even by means of high-resolution NMR spectroscopy. A method to assign the NMR signals of these unstable complexes through a combination of selective isotope labeling of amino acids in a protein and site-specific labeling the protein with a paramagnetic tag is presented herein. By using this method, the resonances of unstable thioester intermediate complex (lifetime <5 h and highest concentration ≈20 μm ) generated by Staphylococcus aureus sortase A and its peptide substrate under a real-time reaction have been assigned.     

Ru-doped 3D porous Ni3N sphere as efficient Bi-functional electrocatalysts toward urea assisted water-splitting

Developing efficient, stable and ideal urea oxide (UOR) electrocatalyst is key to produce green hydrogen in an economical way. Herein, Ru doped three dimensional (3D) porous Ni₃N spheres, with tannic acid (TA) and urea as the carbon and nitrogen resources, is synthesized via hydrothermal and low-temperature treated process (Ru–Ni₃N@NC). The porous nanostructure of Ni₃N and the nickel foam provide abundant active sites and channel during catalytic process. Moreover, Ru doping and rich defects favor to boost the reaction kinetics by optimizing the adsorption/desorption or dissociation of intermediates and reactants. The above advantages enable Ru–Ni₃N@NC to have good bifunctional catalytic performance in alkaline media. Only 43 and 270 mV overpotentials are required for hydrogen evolution (HER) and oxygen evolution (OER) reactions to drive a current of 10 mA cm^?2. Moreover, it also showed good electrocatalytic performance in neutral and alkaline seawater electrolytes for HER with 134 mV to drive 10 mA cm^?2 and 83 mV to drive 100 mA cm^?2, respectively. Remarkably, the as-designed Ru–Ni₃N@NC also owns extraordinary catalytic activity and stability toward UOR. Moreover, using the synthesized Ru–Ni₃N@NC nanomaterial as the anode and cathode of urea assisted water decomposition, a small potential of 1.41 V was required to reach 10 mA cm^?2. It can also be powered by sustainable energy sources such as wind, solar and thermal energies. In order to make better use of the earth's abundant resources, this work provides a new way to develop multi-functional green electrocatalysts.     

Cyclodextrin-Based Multistimuli-Responsive Supramolecular Assemblies and Their Biological Functions

Cyclodextrins (CDs), which are a class of cyclic oligosaccharides extracted from the enzymatic degradation of starch, are often utilized in molecular recognition and assembly constructs, primarily via host–guest interactions in water. In this review, recent progress in CD-based supramolecular nanoassemblies that are sensitive to chemical, biological, and physical stimuli is updated and reviewed, and intriguing examples of the biological functions of these nanoassemblies are presented, including pH- and redox-responsive drug and gene delivery, enzyme-activated specific cargo release, photoswitchable morphological interconversion, microtubular aggregation, and cell–cell communication, as well as a geomagnetism-controlled nanosystem for the suppression of tumor invasion and metastasis. Moreover, future perspectives and challenges in the fabrication of intelligent CD-based biofunctional materials are also discussed at the end of this review, which is expected to promote the translational development of these nanomaterials in the biomedical field.     

Numerical analysis of propagation of thermal disturbances in brass-stabilized REBCO tapes

An extensive characterization of commercially available High-Temperature Superconducting (HTS) REBCO tapes has been recently performed at KIT. The main thermo-physical properties of the tapes have been measured, and heat slug and quench propagation have been investigated in vacuum at LN₂ temperature, using a resistive heater as driver and recording the voltage and temperature evolution after the pulse at several locations along the tapes.In this paper, we present a study of thermal disturbance propagation in a HTS tape with brass stabilizer. The experimental data are analyzed first, to identify the phenomena that influence heat propagation in the tape, and namely the heat loss to the sample holder and the non-ideal efficiency of the resistive heater. A numerical tool is then developed, which solves the 1D transient heat conduction equation in each layer of the tape and accounts for the thermal coupling between layers. The heat loss to the sample holder and the non-ideal efficiency of the resistive heater are taken into account in the model.A first validation of the thermal part of the model against an extended database of heat slug propagation tests is then performed: the comparison between simulation and experiment confirms the very good capability of the model to reproduce the measured temperature evolution. Finally, the results of the simulations of quench propagation are compared with experimental data, showing the capability of the model to reproduce the experiment, within the uncertainty in the input parameters.     

A synergistic effect between nanoconfinement of carbon aerogels and catalysis of CoNiB nanoparticles on dehydrogenation of LiBH4

A synergistic effect of nanoconfinement and catalyzing is a new strategy to enhance the dehydrogenation properties of complex hydrides. Herein, LiBH₄ has been infiltrated into a CoNiB-loaded carbon aerogels system (donated as LiBH₄@CA@CoNiB). It is found that the desorption performances of LiBH₄ are significantly strengthened. The onset desorption temperature of LiBH₄@CA@CoNiB is decreased to 192 °C, and majority of the liberation occurs at about 320 °C, much lower than that of pure LiBH₄. Also, about 15.9 wt% H₂ could be released below 600 °C. Furthermore, LiBH₄ doped with CA@CoNiB exhibits an excellent desorption kinetics, with a capacity of 9.33 wt% H₂ released in 30 min at 350 °C, while only 2.13 wt% H₂ is gained for bulk LiBH₄. In addition, the apparent activation energy (Ea) is reduced sharply from 59.00 kJ/mol (pure LiBH₄) to 46.39 kJ/mol.