Anti-bacterial effect of four extracts from leaves of Dracontomelon dao on Escherichia coli growth using microcalorimetry coupled with principal component analysis

The anti-Escherichia coli activities of four extracts in leaves of Dracontomelon dao, a traditional folk herb in China were investigated and compared by microcalorimetry. The four extracts are PE fraction, CHCl₃ fraction, EtOAc fraction, and n-BuOH fraction. The heat flow power–time (HFP–time) curves of E. coli growth in the presence of the four extracts were measured using an ampoule method. Then the nine thermal kinetic parameters were obtained from the curves. From the result of principal component analysis, it can be seen that parameters k ₁, k ₂, P ₁, and Q _p2 might be the main parameters in evaluating the anti-E. coli effects. In the presence of CHCl₃ fraction, EtOAc fraction, and n-BuOH fraction, k ₂, Q _p2 of E. coli decreased with increasing concentrations of the extracts. The EtOAc fraction was observed to have the strongest anti-bacterial activity with half-inhibitory concentration IC50 of 98.5 μg mL^?1. So, it can be concluded that EtOAc fraction can be further developed as anti-bacterial bioactive fraction of leaves of Dracontomelon dao.     

Effect of formation factors on light crude oil oxidation via TG-FTIR

This research aimed at the investigation of the effect of formation factors on the light crude oil during the high temperature air injection process. For this purpose, thermogravimetric and Fourier Transform Infrared Spectroscopy techniques were combined to investigate the light crude oil and oil mixed with formation water and sand at 58, 250, and 450 °C, respectively. The results showed that at different temperature range, the mass drop rate presented different trend and the formation water and sand increased the activation energy of the oxidation reaction. The formation sand exhibited the excellent catalytic effect at relative low temperature. The oxygen addition reaction massively was trigged at 250 °C, and the bond scission reaction dominated at 450 °C. With different additives at different temperature range, the type, concentration, and produced timing of the products presented different tendency.     

A novel electrochemiluminescence glucose biosensor based on platinum nanoflowers/graphene oxide/glucose oxidase modified glassy carbon electrode

A novel electrochemiluminescence (ECL) biosensor based on platinum nanoflowers (PtNFs)/graphene oxide (GO)/glucose oxidase (GODx) was discovered for glucose detection. PtNFs/GO was synthesized using a nontoxic, rapid, one-pot and template-free method and characterized by transmission electron microscopy (TEM) and high-resolution TEM techniques. The as-prepared PtNFs/GO with clean surface and multiporous structure was used to assemble GODx to form a glucose biosensor. Based on ECL results, the PtNFs/GO/GODx film-modified electrode displayed a high electrocatalytic activity towards the oxidation of glucose, which generated hydrogen peroxide (H₂O₂) to react with the luminol radicals thus enhanced the luminol ECL. Under the optimized conditions, two linear regions of ECL intensity to glucose concentration were valid in the range from 5 to 80 μmol/L (r?=?0.9957) and 80 to 1,000 μmol/L (r?=?0.9909) with a detection limit (S/N?=?3) of 2.8 μmol/L. In order to verify the reliability, the thus-fabricated biosensor was applied to determine the glucose concentration in glucose injection, glucose functional drink, and blood serum. The results indicated that the proposed biosensor presented good characteristics in terms of high sensitivity and good reproducibility for glucose determination, promising the applicability of this sensor in practical analysis.     

Activated nitrogen-doped carbons from polyvinyl chloride for high-performance electrochemical capacitors

Activated nitrogen-doped carbons (ANCs) were prepared by carbonization/activation approach using aminated polyvinyl chloride (PVC) as precursor. ANCs exhibit larger porosities and higher specific surface areas than those of their nitrogen-free counterparts for the same KOH/carbon ratio. The specific surface area of ANC-1 is up to 1,398 m² g^?1 even at a low KOH/carbon ratio of 1:1. Fourier transform infrared spectroscopy investigation of the nitrogen-enriched resin precursor indicates the efficient dehydrochlorination of PVC by ethylenediamine at a low temperature. The nitrogen content and the population of nitrogen functionalities strongly depend on the KOH/carbon ratios and decrease drastically after KOH activation as seen from the elemental and X-ray photoelectron spectroscopy analysis. The surface concentration of N-6 and N-Q almost disappears and the dominant nitrogen groups become N-5 after KOH activation. The highest specific capacitance of ANCs is up to 345 F g^?1 at a current density of 50 mA g^?1 in 6 M KOH electrolyte. ANCs also exhibit a good capacitive behavior at a high scan rate of 200 mV s^?1 and an excellent cyclability with a capacitance retention ratio as high as ～93 % at a current density of 2,000 mA g^?1 for 5,000 cycles.     

Chemoselective Catalytic Conjugate Addition of Alcohols over Amines

A highly chemoselective conjugate addition of alcohols in the presence of amines is described. The cooperative nature of the catalyst enabled chemoselective activation of alcohols over amines, allowing the conjugate addition to soft Lewis basic α,β‐unsaturated nitriles. Divergent transformation of the nitrile functionality highlights the utility of the present catalysis.     

Restraint of stress in fabricating the large areas of crack-free porous silica films in the presence of composite polydimethylsiloxane

To present a new method of fabricating the large areas of crack-free porous silica films by introduction of composite polydimethylsiloxanes (PDMS). We employed two kinds of side-chain polyether modified by PDMS terminated with Si–CH₃ and Si–OC₂H₅ groups in preparation of large areas of porous silica films. The porous film presents a mesopore structure with a porosity of 58.0 %, which is fit for thermal-isolating layer applied in pyroelectric devices. The stress evolution on gel-to-ceramic film conversion has been investigated. The results reveal that a slow decrease in tensile stress before 250 °C and a slow increase after 250 °C can be observed, which is closely related to the alteration of chemical composition in the heat-treatment process. It is clear that the stress has been restrained with the addition of composite PDMS.     

Highly Enantioselective Ring‐Opening Reactions of Aziridines with Indole and Its Application in the Building of C3‐Halogenated Pyrroloindolines

A magnesium‐catalyzed asymmetric ring‐opening reaction of aziridine with indole has been realized by employing commercially available chiral ligands. Both of the enantiomers of the ring‐opening product could be obtained with good yields and a high level of enantioselectivity. The corresponding ring‐opening product could be further transformed to various types of enantioenriched C₃‐halogenated‐pyrroloindolines.     

Nickel‐Catalyzed Site‐Selective Amidation of Unactivated C(sp3)H Bonds

Intramolecular dehydrogenative cyclization of aliphatic amides was achieved on unactivated sp³ carbon atoms by a nickel‐catalyzed C?H bond functionalization process with the assistance of a bidentate directing group. The reaction favors the C?H bonds of β‐methyl groups over the γ‐methyl or β‐methylene groups. Additionally, a predominant preference for the β‐methyl C?H bonds over the aromatic sp² C?H bonds was observed. Moreover, this process also allows for the effective functionalization of benzylic secondary sp³ C?H bonds.     

Rationally Investigating the Influence of T1 Location on Electroluminescence Performance of Aryl Amine Modified Phosphine Oxide Materials

The correspondence between triplet location effect and host‐localized triplet–triplet annihilation and triplet–polaron quenching effects was performed on the basis of a series of naphthyldiphenylamine (DPNA)‐modified phosphine oxide hosts. The number and ratio of DPNA and diphenylphosphine oxide was adjusted to afford symmetrical and unsymmetrical molecular structures and different electronic environments. As designed, the first triplet (T₁) states were successfully localized on the specific DPNA chromophores. Owing to the meso‐ and multi‐insulating linkages, identical optical properties and comparable electrical performance was observed, including the same first singlet (S₁) and T₁ energy levels to support the similar singlet and triplet energy transfer and the close frontier molecular orbital energy levels. This established the basis of rational investigation on T₁ location effect without interference from other optoelectronic factors.     

Cerium‐Based M4L4 Tetrahedra as Molecular Flasks for Selective Reaction Prompting and Luminescent Reaction Tracing

The application of metal–organic polyhedra as “molecular flasks” has precipitated a surge of interest in the reactivity and property of molecules within well‐defined spaces. Inspired by the structures of the natural enzymatic pockets, three metal–organic neutral molecular tetrahedral, Ce‐TTS, Ce‐TNS and Ce‐TBS (H₆TTS: N′,N′′,N′′′‐nitrilotris‐4,4′,4′′‐(2‐hydroxybenzylidene)‐benzohydrazide; H₆TNS: N′,N′′,N′′′‐nitrilotris‐6,6′,6′′‐(2‐hydroxybenzylidene)‐2‐naphthohydrazide; H₆TBS: 1,3,5‐ phenyltris ‐4,4′,4′′‐(2‐hydroxybenzylidene)benzohydrazide), which exhibit different size of the edges and cavities, were achieved through self‐assembly by incorporating robust amide‐containing tridentate chelating sites into the fragments of the ligands. They acted as molecular flasks to prompt the cyanosilylation of aldehydes with excellent selectivity towards the substrates size. The amide groups worked as trigger sites and catalytic driven forces to achieve efficient guest interactions, enforcing the substrates proximity within the cavity. Experiments on catalysts with the different cavity radii and substrates with the different molecular size demonstrated that the catalytic performance exhibited enzymatical catalytic mechanism and occurred in the molecular flask. These amides were also able to amplify guest‐bonding events into the measurable outputs for the detection of concentration variations of the substrates, providing the possibility for metal–organic hosts to work as smart molecular flasks for the luminescent tracing of catalytic reactions.