11B and 15N solid state NMR investigation of a boron nitride preceramic polymer prepared by ammonolysis of borazine

A poly(aminoborazine), precursor for hexagonal boron nitride (h-BN) obtained by reaction of borazine B₃N₃H₆ with ammonia, and its pyrolysis derivatives have been extensively characterised by ¹⁵N and ¹¹B MAS NMR. The various B and N sites have been identified according to their first neighbouring atoms, as well as to the second ones in the case of ¹⁵N, and have also been quantified. This study demonstrates that a suitable choice of NMR techniques together with the use of isotopic enrichment can lead to a large improvement in spectral resolution, which allows a better understanding of such complex BN preceramic polymer structures and permits to follow the polymer-to-ceramic transformation.     

Variation of the photoluminescence and vacuum ultraviolet excitation characteristics of BaZr(BO3)2:Eu3+ by the incorporation of Al3+, La3+, or Y3+ into the lattice

The photoluminescence (PL) and vacuum ultraviolet (VUV) excitation properties are studied for the BaZr(BO₃)₂:Eu³⁺ phosphor with incorporating the Al³⁺, La³⁺, or Y³⁺ ion into the lattice. The excitation spectrum shows an absorption band in the VUV region with the band-edge at 200 nm and a very weak charge transfer band of Eu³⁺ at about 226 nm. The luminescence spectrum shows a strong emission at 615 nm (⁵D₀ → ⁷F₂ transition) and weak emission at 594 nm (⁵D₀ → ⁷F₁ transition) in BaZr(BO₃)₂:Eu³⁺, with a good red color purity. The PL intensity is increased by incorporating Al³⁺ into the BaZr(BO₃)₂ lattice. The PL intensity has also increased by incorporating La³⁺ into the lattice, however, the red color purity has deteriorated because of the increased centrosymmetric nature of the site. With the incorporation of Y³⁺ into the BaZr(BO₃)₂ lattice, the PL characteristics of the Eu³⁺ activator resembles that in the YBO₃ lattices. The intensity of the red PL for the Eu³⁺ activator is the highest with good color purity for BaZr(BO₃)₂:Eu³⁺ incorporated with both Al³⁺ (10%) and La³⁺ (0.5%).     

Au nanoparticles decorated on magnetic nanocomposite (GO-Fe3O4/Dop/Au) as a recoverable catalyst for degradation of methylene blue and methyl orange in water

In the present research, magnetically recyclable graphene oxide (GO)/dopamine hydrochloride/AuNPs nanocatalyst are prepared by a green path with Acorus calamus seeds extract as a stabilizing and reducing agent and its catalytic efficiency was used for the reduction of methylene blue (MB) and methyl orange (MO) in the presence of NaBH₄ as a reducing agent in the aqueous medium in the ambient conditions. The prepared nanocatalyst was characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR) spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and UV–Vis spectroscopy. The prepared nanocatalyst has good catalytic activity and can be regain by an external magnet and recycled several times without considerable loss of its catalytic activity in the process of reduction of organic dyes.     

One-pot synthesis of PdBi/reduced graphene oxide catalyst under microwave irradiation used for formic acid electrooxidation

The Pd and PdBi nanoparticles dispersed on the reduced graphene oxide (Pd/rGO and PdBi/rGO) have been synthesized through one-pot reaction under the irradiation of microwave and the obtained composites have been characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and their electrocatalytic activities have also been evaluated. It is found that the PdBi_0.05/rGO catalyst exhibits higher activity and better stability toward formic acid electrooxidation compared with Pd/C and Pd/rGO. The excellent electrocatalytic performance indicates that the addition of appropriate amount of Bi can greatly enhance the activity and stability of Pd catalysts for the formic acid oxidation.     

Enabled/disabled predicate encryption in clouds

Predicate encryption is a cryptographic primitive that provides fine-grained control over access to encrypted data. It is often used for encrypted data search in a cloud storage environment. In this paper, we propose an enabled/disabled predicate encryption scheme, which is the first work that provides timed-release services and data self-destruction (they correspond to the terms “enabled” and “disabled,” respectively). Owing to these properties, the sender can set the readable/unreadable time of the files to be sent to the receiver. The receiver can read the sent file only after the readable time. After the unreadable time, the structure of the file will be destroyed and the file will become unreadable. Furthermore, for practical usage purposes, the extended scheme, which is based on the proposed scheme, provides not only timed-release services and data self-destruction but also long message encryption and undecryptable search. In the extended scheme, the length of encrypted messages does not depend on the order of the group. Moreover, the cloud server can obtain only the matched ciphertexts after the search.     

Comparison of dipeptidyl peptidase IV-inhibitory activity of peptides from bovine and caprine milk casein by in silico and in vitro analyses

The different potential for release of dipeptidyl peptidase IV (DPP-IV)-inhibitory peptides from bovine and caprine milk casein was assessed by in silico analysis and in vitro proteolytic assays. The former predicted a weakly higher potency for caprine casein than bovine as a precursor of DPP-IV-inhibitory peptides, although with markedly diverse potential for individual caseins. This was verified by protease hydrolysis; trypsin-treated casein hydrolysates (TCAHs) displayed the strongest bioactivity. Fractionation of caprine TCAHs revealed slightly, but significantly, higher inhibitory activity in peptides <5 kDa, and notably greater efficiency in the >5 kDa fraction, than their bovine counterparts. Through in silico trypsin hydrolysis and peptides synthesis, four novel caprine casein-derived DPP-IV-inhibitory peptides, including GPFPILV and HPINHR (half maximal inhibitory concentration = 163.7 ± 1.33 and 452.2 ± 7.15 μm, respectively), were found. This study corroborates the weak superiority of caprine casein over bovine in release of DPP-IV-inhibitory peptides, and identifies several novel caprine casein-derived DPP-IV-inhibitory peptides.     

Simple self-assembly of SnS2 entrapped graphene aerogel and its enhanced lithium storage performance

In this work, SnS₂ nanoplates entrapped graphene aerogel has been successfully prepared by simple self-assembly of reduced graphene oxide obtained through mild chemical reduction. Structural and morphological investigations demonstrated that SnS₂ nanoplates are highly dispersed in the three dimensional (3D) porous graphene matrix. When served as anode material for lithium-ion batteries, the electrochemical properties of SnS₂/graphene aerogel (SnS₂/GA) were evaluated by galvanostatic discharge–charge tests, cyclic voltammetry and impedance spectroscopy measurement. Compared with pristine SnS₂, the SnS₂/GA nanocomposite achieved a much higher initial reversible capacity (1186 mAh g⁻¹), superior cyclic stability (1004 mAh g⁻¹ after 60 cycles, corresponding to 84.7% of the initial reversible capacity), as well as better rate capability (650 mAh g⁻¹ at a current density of 1000 mA g⁻¹). This significantly improved lithium storage performance can be attributed to the good integration of SnS₂ nanoplates with 3D porous graphene network, which can not only provide much more active sites and easy access for Li ions intercalation, but also prevent the aggregation of SnS₂ nanoplates and facilitate fast transportation of Li ions and surface electrons during the electrochemical process.     

Enhanced emission and improved thermal stability of BaMgAl10O17:Eu2+ phosphor via additional Mg2+ doping

BaMgAl₁₀O₁₇:Eu²⁺ doped with 0–6% additional Mg²⁺ were synthesized by co-precipitation method. Their photoluminescence and thermal stability were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation. The additional Mg²⁺-doped samples exhibited stronger emission intensity and better thermal stability than the sample without additional Mg²⁺ under 254 or 147 nm excitation. After thermal degradation, the 4% additional Mg²⁺-doped sample had the highest emission intensity which was 12.7% and 16.6% stronger than that of the sample without additional Mg²⁺ under 254 and 147 nm excitation, respectively. Moreover, the improvement mechanisms on emission intensity and thermal stability were discussed.     

Boron removal by hydrotalcite-like,carbonate-free Mg–Al–NO3-LDH and a rationale on the mechanism

Removal of boron from boric acid and tetraborate solutions by hydrotalcite (HT)-like, carbonate-free, Mg–Al–NO₃-layered double hydroxide (LDH) was studied. Data from batch experiments were computed as a function of the adsorbent dose and contact time. Synthesis in CO₂-free conditions provided a material with high anion exchange capacity and more than 95% adsorption could be achieved. The physical and structural properties of the material before and after boron adsorption were investigated to describe the uptake mechanism. Interpretation of the results of d-spacing, surface area and zeta potential measurements indicated an anion exchange mechanism rather than surface adsorption. Calcination at 400 °C did not make any significant change in the removal process.