Structure and dielectric properties of 80%Pb(Zn1/3Nb2/3)O3–20%PbTiO3 thin films prepared by modified sol–gel process

80%Pb(Zn_1/3Nb_2/3)O₃–20%PbTiO₃ (PZN–PT) thin films have been prepared on Pt/Ti/SiO₂/Si substrates using a modified sol–gel method. In our method, niobium pentaoxide is used as a substitution instead of niobium ethoxide which is moisture-sensitivity and much more expensive. Microstructure and electrical properties of PZN–PT thin films have been investigated. X-ray diffraction analysis shows that proper annealing temperature of PZN–PT thin films is 600 °C. The PZN–PT thin films annealed at 600 °C are polycrystalline with (111)-preferential orientations. Field-emissiom scanning electron microscope analysis revealed PZN–PT thin films possess well-defined and crack-free microstructure. The thickness of thin films is 290 nm. The Pt/PZN–PT/Pt capacitors have been fabricated and it presents ferroelectric nature. The remanent polarization (Pr), spontaneous polarization (Ps), and the coercive electric field (Ec) are 8.71 μC/cm², 43.06 μC/cm², and 109 kV/cm at 1 MHz, respectively. The dielectric constant (ε_r) and the dissipation factor (tan δ) are about 500.3 and 0.1 at 1 kHz, respectively.     

Asymmetric vinylogous Mannich reactions: a versatile approach to functionalized heterocycles

Asymmetric vinylogous Mannich reaction (VMR) of 2-(tert-butyldimethylsilyloxy)furan (TBSOF, 1) with (R(S))- or (S(S))-t-BS-imines (3) furnished 5-aminoalkylbutenolides 7a-k in 75-87% yields with anti/syn ratios ranging from 75:25 to 97:3. Butenolides 7a-f,k were readily converted into substituted lactones 8 and 5 and 6-substituted 5-hydroxypiperidin-2-ones 11a-g, which are, in turn, key intermediates for the synthesis of many bioactive compounds.     

A new aminopeptidase inhibitor from Streptomyces strain HCCB10043 found by UPLC-MS

The diversity of microbial metabolites has been of interest and concern for a long time, yet a suitable method for discovering these is still unavailable. In the work discussed in this report, ultra-performance liquid chromatography coupled with tandem quadrupole and time of flight high-resolution mass spectrometry (UPLC–Q–TOF-HRMS), with MS data analysis, was set up to study the metabolites of Streptomyces strain HCCB10043. It was found that besides antibacterial substances (A21978C complex) and two anti-aminopeptidase compounds (valistatin and bestatin), this strain can produce a new aminopeptidase inhibitor, identified as 3-amino-2-hydroxy-4-phenylbutanoylvalylisoleucine. This new compound had greater activity than valistatin or bestatin in aminopeptidase N (APN) inhibition assay. The results proved that combination of UPLC–Q–TOF-MS analysis and classic purification and identification steps as complementary strategies can provide a method with high reliability for research on microbial secondary metabolites. Furthermore, it has shown that the study of secondary metabolic profiling might be the key to discovering new drugs.     

A ratiometric luminescent sensing of Ag+ ion via in situ formation of coordination polymers

A ratiometric luminescent sensing of Ag(+) ion is developed via the Ag(I)-NCys coordination polymeric luminophore in situ formed in aqueous solution upon mixing Ag(+) ion with the designed fluorescent thiol ligand NCys.     

Scanned chemical enhancement of surface-enhanced Raman scattering using a charge-transfer complex

We have fabricated a charge-transfer system using the self-assembly method. We find the nontotally symmetric b(2) modes are selectively enhanced in SERS spectroscopy and represent a laser wavelength-dependent property.     

In Situ Raman Monitoring and Manipulating of Interfacial Hydrogen Spillover by Precise Fabrication of Au/TiO2/Pt Sandwich Structures

The spillover of hydrogen species and its role in tuning the activity and selectivity in catalytic hydrogenation have been investigated in situ using surface‐enhanced Raman spectroscopy (SERS) with 10 nm spatial resolution through the precise fabrication of Au/TiO₂/Pt sandwich nanostructures. In situ SERS study reveals that hydrogen species can efficiently spillover at Pt‐TiO₂‐Au interfaces, and the ultimate spillover distance on TiO₂ is about 50 nm. Combining kinetic isotope experiments and density functional theory calculations, it is found that the hydrogen spillover proceeds via the water‐assisted cleavage and formation of surface hydrogen–oxygen bond. More importantly, the selectivity in the hydrogenation of the nitro or isocyanide group is manipulated by controlling the hydrogen spillover. This work provides molecular insights to deepen the understanding of hydrogen activation and boosts the design of active and selective catalysts for hydrogenation.     

A Glycosylated Cationic Block Poly(β‐peptide) Reverses Intrinsic Antibiotic Resistance in All ESKAPE Gram‐Negative Bacteria

Carbapenem‐resistant Gram‐negative bacteria (GNB) are heading the list of pathogens for which antibiotics are the most critically needed. Many antibiotics are either unable to penetrate the outer‐membrane or are excluded by efflux mechanisms. Here, we report a cationic block β‐peptide (PAS8‐b‐PDM12) that reverses intrinsic antibiotic resistance in GNB by two distinct mechanisms of action. PAS8‐b‐PDM12 does not only compromise the integrity of the bacterial outer‐membrane, it also deactivates efflux pump systems by dissipating the transmembrane electrochemical potential. As a result, PAS8‐b‐PDM12 sensitizes carbapenem‐ and colistin‐resistant GNB to multiple antibiotics in vitro and in vivo. The β‐peptide allows the perfect alternation of cationic versus hydrophobic side chains, representing a significant improvement over previous antimicrobial α‐peptides sensitizing agents. Together, our results indicate that it is technically possible for a single adjuvant to reverse innate antibiotic resistance in all pathogenic GNB of the ESKAPE group, including those resistant to last resort antibiotics.     

Recent Development on Controlled Synthesis of Metal Sulfides Hollow Nanostructures via Hard Template Engaged Strategy: A Mini‐Review

In this mini‐review, we highlighted the recent progresses in the controlled synthesis of metal sulfides hollow nanostructures via hard template technique. After a brief introduction about the formation mechanism of the inorganic hollow nanostructures via hard template technique, the discussions primarily focused on the emerging development of metal sulfides hollow nanostructures. Various synthetic strategies were summarized concerning the use of the hard template engaged strategies to fabricate various metal sulfides hollow nanostructures, such as hydrothermal method, solvothermal method, ion‐exchange, sulfidation or calcination etc. Finally, the perspectives and summaries have been presented to demonstrate that a facile synthetic technique would be widely used to fabricate metal sulfides hollow nanostructures with multi‐shells and components.     

Electron Microscopy Studies of Local Structural Modulations in Zeolite Crystals

Zeolites are widely used in catalysis, gas separation, ion exchange, etc. due to their superior physicochemical properties, which are closely related to specific features of their framework structures. Although more than two hundred different framework types have been recognized, it is of great interest to explore from a crystallographic perspective, the atomic positions, surface terminations, pore connectivity and structural defects that deviate from the ideal framework structures, namely local structural modulation. In this article, we review different types of local modulations in zeolite frameworks using various techniques, especially electron microscopy (EM). The most recent advances in resolving structural information at the atomic level with aberration corrected EM are also presented, commencing a new era of gaining atomic structural information, not only for all tetrahedral atoms including point vacancies in framework but also for extra-framework cations and surface terminations.