Visualization and In Situ Ablation of Intracellular Bacterial Pathogens through Metabolic Labeling

Protected by the host cells, the hidden intracellular bacteria are typically difficult to kill by common antibiotics and cannot be visualized without complex cellular pretreatments. Herein, we successfully developed a bacteria-metabolizable dual-functional probe TPEPy-d -Ala, which is based on d -alanine and a photosensitizer with aggregation-induced emission for fluorescence turn-on imaging of intracellular bacteria in living host cells and photodynamic ablation in situ. Once metabolically incorporated into bacterial peptidoglycan, the intramolecular motions of TPEPy-d -Ala are inhibited, leading to an enhanced fluorescent signal, which allows the clear visualization of the intracellular bacteria. Moreover, TPEPy-d -Ala can effectively ablate the labeled intracellular bacteria in situ owing to covalent ligation to peptidoglycan, yielding a low intracellular minimum inhibitory concentration (MIC) of 20±0.5 μg mL⁻¹, much more efficient than that of a commonly used antibiotic, vancomycin.     

Unveiling the Activity Origin of a Copper-based Electrocatalyst for Selective Nitrate Reduction to Ammonia

Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. ¹⁵N isotope labeling experiments showed that ammonia originated from nitrate reduction. ¹H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu₂O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu₂O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.     

Nickel (II) tetrapyridyl complexes as electrocatalysts and precatalysts for water oxidation

Two nickel complexes, [Ni(tpen)](ClO₄)₂.0.5CH₃COCH₃ ( 1 ) and [Ni(tpbn)](ClO₄)₂ ( 2 ), of tetrapyridyl ligands N,N,N′,N′-tetrakis(2-pyridyl-methyl)-1,2-ethanediamine (tpen) and N,N,N′,N′-tetrakis(2-pyridyl-methyl)-1,4-butanediamine (tpbn) were prepared and their catalysis for water oxidation reaction (WOR) studied. In 0.1 M phosphate buffer solution (PBS) of pH 8.0, complex 1 is a homogeneous molecular catalyst with an overpotential of ~440 mV and a Faradaic efficiency of 89%. At pH ≥ 9.0, complex 1 degraded gradually during the catalytic process and formed NiO_x composite (nickel oxide with general formula Ni_xO_yH_z) active for WOR. In contrast, complex 2 deteriorated under measured conditions (pH 8.0–12.0) and formed NiO_x composite active for WOR. The NiO_x composite derived from 1 in 0.1 M PBS at pH 11.0 showed an activity with an overpotential of ~500 mV, a Tafel slope of ~90 mV/decade and a Faradaic efficiency of 97%. Mechanisms were proposed for water oxidation catalyzed by 1 and 2 . This work revealed that the catalytic activity of the nickel complexes was related to the flexibility of the tetrapyridyl ligands and the adaptability of the coordination sphere of the nickel(II) center.     

Effects of hydroxyethyl methyl cellulose ether on the hydration and compressive strength of calcium aluminate cement

Journal of Thermal Analysis and Calorimetry - Aluminate containing phases such as tricalcium aluminate (C3A) and dodecacalcium heptaaluminate (C12A7) play a key role in the reaction between...     

Designed synthesis of ZnO/PEDOT core/shell hybrid nanotube arrays with enhanced electrochromic properties

Designed growth of zinc oxide (ZnO)/poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell hybrid nanotube arrays has been achieved by electropolymerization technique. The ZnO/PEDOT hybrid nanotubes electropolymerized for 2000-second display enhanced electrochromic properties of the contrast ratio up to 31.3%, a lot higher than those of the pure PEDOT and ZnO/PEDOT hybrid nanorods. Moreover, the coloring efficiency of the hybrid nanotubes increases from 105.2 cm² C⁻¹ of ZnO/PEDOT hybrid nantotube with the electrodeposition time of 1000 seconds to 122.2 cm² C⁻¹ of 2000 seconds at 520 nm. Therefore, the hybrid composite nanotubes fabricated by the in situ electrodeposition techniques may demonstrate huge potential applications in energy-saving technologies such as smart windows.     

Structurally Interesting Diarymethane Derivatives from Securidaca inappendiculata

Securines A—E, three dimeric diarymethane derivatives ( 1 — 3 ) and two enantiomeric diarymethane derivative monomers ( 4 and 5 ), were isolated and characterized from the medicinal plant Securidaca inappendiculata. Compounds 1 and 2 are a pair of enantiomeric diarymethane derivative dimers, and compound 3 is a mesomeric diarymethane derivative dimer. Their structures were determined by a combination of spectroscopic data, X‐ray crystallography, electronic circular dichroism (ECD) analysis, and computational ECD calculations. Dimeric compounds 1 — 3 showed moderate antiplasmodial activities with IC₅₀ values of 0.9, 1.4, and 1.5 μM, respectively.     

1,1′‐[(Ethane‐1,2‐diyldioxy)di‐o‐phenylene]bis(indoline‐2,3‐dione) (L) and a novel [Ag2L2]2+ metallocycle based on coordination‐driven Ag—O and Ag—π bonds

1,1′‐[(Ethane‐1,2‐diyldioxy)di‐o‐phenylene]bis(indoline‐2,3‐dione), C₃₂H₂₄N₂O₆, L or (I), adopts a trans conformation with the two terminal indoline‐2,3‐dione groups located on opposite sides of the central ether bridge, as required by a centre of inversion located at the mid‐point of the ethane C—C bond. However, in the discrete binuclear Ag^I metallocycle complex salt bis{μ‐1,1′‐[(ethane‐1,2‐diyldioxy)di‐o‐phenylene]bis(indoline‐2,3‐dione)}disilver(I) bis(hexafluoridoantimonate), [Ag₂(C₃₂H₂₄N₂O₆)₂][SbF₆]₂, (II), synthesized by combination of L with AgSbF₆, L adopts a gauche conformation to bind Ag^Ivia the two indolinedione O atoms and two C atoms from the phenoxy ring. One dione O atom from the opposite side of the ether bridge completes the irregular coordination environment of each Ag^I atom. The complex is on a centre of inversion located between the Ag^I atoms. In the solid state, these binuclear [Ag₂L₂]²⁺ metallocycles stack together via intermolecular π–π interactions to generate a one‐dimensional chain motif, with the [SbF₆]⁻ counter‐ions, which are disordered, located between the chains.     

A density functional theory approach to mushroom-like platinum clusters on palladium-shell over Au core nanoparticles for high electrocatalytic activity

Recently, it was found that Pt clusters deposited on Pd shell over Au core nanoparticles (Au@Pd@Pt NPs) exhibit unusually high electrocatalytic activity for the electro-oxidation of formic acid (P. P. Fang, S. Duan, et al., Chem. Sci., 2011, 2, 531-539). In an attempt to offer an explanation, we used here carbon monoxide (CO) as probed molecules, and applied density functional theory (DFT) to simulate the surface Raman spectra of CO at this core-shell-cluster NPs with a two monolayer thickness of Pd shell and various Pt cluster coverage. Our DFT results show that the calculated Pt coverage dependent spectra fit the experimental ones well only if the Pt clusters adopt a mushroom-like structure, while currently the island-like structure is the widely accepted model, which follows the Volmer-Weber growth mode. This result infers that there should be a new growth mode, i.e., the mushroom growth mode as proposed in the present work, for Au@Pd@Pt NPs. We suggest that such a mushroom-like structure may offer novel active sites, which accounts for the observed high electrocatalytic activity of Au@Pd@Pt NPs.     

Electrochemiluminescence Behavior of Ru(bpy)32+/Carbofuran System on an Electrically Heated Microelectrode Chip

An electrically heated microelectrode chip (HMEC) was designed and the Ru(bpy)₃²⁺/carbofuran electrochemiluminescence (ECL) systems were applied to characterize the performance of the HMEC. The ECL intensities increase at elevated electrode temperature, and the detection limit at 60°C (electrode surface temperature) was about 10 times lower than that at 30°C. The results indicate that new heated electrode can be handled easily and can be mass produced, the difference between the electrodes was little. The stability of the HMEC was good since the electrode surface can hardly be destroyed during detection and storage.     

Enhanced ordering in gold nanoparticles self-assembly through excess free ligands

Self-assembly of nanometer-sized particles is an elegant and economical approach to achieve dense patterns over large areas beyond the resolution and throughput capabilities of electron-beam lithography. In this paper, we present results of self-assembly of oleylamine-capped gold nanoparticles with 8.0 ± 0.3 nm diameter into densely packed and well-ordered monolayers with center-to-center distance of ～11 nm. Self-assembly was done in a Langmuir-Blodgett trough and picked up onto Si substrates. The nanoparticles undesirably assembled within micrometer-sized "droplets" that were organic in nature. However, within these droplets, we observed that the addition of the excess ligand, oleylamine, drastically enhanced the self-assembly of the nanoparticles into monolayers with near-perfect ordering. This approach has the potential use in templated self-assembly of nanoparticles for rearranging poorly ordered assembly into a commensurate prepatterned substrate.