Amperometric sensing of hydrogen peroxide using a glassy cabon electode modified with silver nanoparticles on poly(alizarin yellow R)

A sensitive amperometric sensor for hydrogen peroxide (HP) was constructed that is based on a glassy carbon electrode (GCE) modified with silver nanoparticles on poly(alizarin yellow R). The polymer was electropolymerized onto the surface of the GCE by cyclic voltammetry (CV), and the AgNPs were then electrodeposited onto its surface. The electrode was characterized by scanning electron microscopy and CV, and used for amperometric determination of HP. The electrode exhibits a favorable catalytic activity towards the reduction of HP, with a linear response range from 1.0???M to 450???M and a detection limit of 0.32???M. The sensor also displays high selectivity, excellent reproducibility, and good long-term stability.

Photocatalysis of PbS quantum dots in a quantum dot-sensitized solar cell: photovoltaic performance and characteristics

PbS QDs have been synthesized by an in situ photocatalysis method using the photocatalytic activity of nanocrystalline TiO(2) films. Both the photovoltaic response and size of the synthesized PbS QDs were analyzed. Compared with the conventional synthesis route, this method is simpler and produces less waste.     

Order-disorder transition in a quasi-two-dimensional colloidal system

A 2D colloidal system governed by repulsive dipolar forces tends to form a more ordered system when the interaction strength between the particles increases. Here we report an order-disorder transition of the colloidal system followed by chain formation upon increasing the dipolar interactions and show that the critical field scales with the density of colloids. Our system can do this by changing its dimensionality and therefore exhibits novel behavior that could help us understand colloidal ordering phenomena.     

Ocular Pharmacokinetic Study of l-Carnosine and N-Acetyl-l-carnosine in Rabbit by Microdialysis Coupled with UPLC-MS-MS

In order to provide useful information for rational drug design, the ocular pharmacokinetics of l-carnosine (CAR) and its acetylized prodrug N-acetyl-l-carnosine (NAC) were investigated. The in vivo microdialysis sampling coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) was developed for continuously simultaneous monitoring of CAR and NAC in rabbit aqueous humor. The measured in vitro recoveries of the probe were 61.3% for CAR and 65.8% for NAC, while in vivo recoveries decreased to 43.1% for CAR and 43.0% for NAC, respectively. The method was sensitive with LLOQ 20.5 ng mL^?1 for CAR and 20.4 ng mL^?1 for NAC. The initial data indicated that the value of C _max and AUC_(0?C??) of NAC were higher than these of CAR (C _max 2305 vs. 1,802 ng mL^?1), (AUC_(0?C??) 1,337 vs. 1,891 ng h mL^?1), which indicated that the NAC exhibited better ocular bioavailability and duration. The method was rapid, specific and sensitive for continuously monitoring of aqueous humor and it was successfully applied to pharmacokinetic studies of CAR and NAC.     

Feeding deterrents against two grain storage insects from Euphorbia fischeriana

The screening of several Chinese medicinal herbs for insecticidal principles showed that Euphorbia fischeriana roots possessed significant feeding deterrent activity against two stored-product insects (Tribolium castaneum and Sitophilus zeamais). From ethanol extract, four feeding deterrents were isolated by bioassay-guided fractionation. The compounds were identified as jolkinolide B, 12-deoxyphorbol 13-(9Z)-octadecenoate 20-acetate, 17-hydroxyjolkinolide A and B on the basis of their phytochemical and spectral data. Jolkinolide B and 17-hydroxyjolkinolide B possessed strong feeding deterrent activities against S. zeamais (EC?? = 342.1 and 543.9 ppm, respectively) and T. castaneum adults (E?? = 361.4 and 551.5 ppm, respectively). 17-Hydroxyjolkinolide A and 12-deoxyphorbol 13-(9Z)-octadecenoate 20-acetate A also exhibited feeding deterrent activity against the two grain storage insects with EC?? values of 631.9 and 884.3 ppm for S. zeamais and 656.5 and 1058.4 ppm for T. castaneum adults.     

Three aromatic amino acids in gastric juice as potential biomarkers for gastric malignancies

For screening early-stage gastric malignancies, the existing serum biomarkers have limited sensitivity and specificity. Gastric juice biomarkers are scarce and require further investigation. We divided this study on searching potential biomarkers into four parts: (1) detection of differential fluorescence spectrum and peaks in the gastric juice from patients using fluorescence spectroscopy and HPLC, (2) identification and validation of differential peaks using LC/MS and NMR, (3) quantification of potential biomarkers, and (4) establishment of diagnostic detection. The fluorescence intensity (FI), tyrosine, phenylalanine, tryptophan and total protein content were significantly higher in the gastric juice of patients with gastric malignancies (all P<0.01). With all P<0.001, the areas under the receiver operating characteristic curves of the biomarkers were tyrosine, 0.838; phenylalanine, 0.856; and tryptophan, 0.816. At a specificity of 79.4%, the sensitivity for gastric malignancy detection with phenylalanine was 87.9% only. Aromatic amino acids in gastric juices could be used as potential diagnostic biomarkers to screen gastric malignancies. It is a less-invasive and economical method compared to gastric biopsy.     

Theoretical elucidation of the rhodium-catalyzed [4 + 2] annulation reactions

The reaction mechanism of the Rh-catalyzed [4 + 2] annulation of 4-alkynals with isocyanates is unraveled using density functional calculations. The reaction mechanisms of the model system and the real substituted system have been investigated and the results are compared. From our theoretical results based on the model and real substituted system, it is shown that (a) the rate-determining step is the Rh-H addition to the alkyne, (b) the formation of the cyclopentenone G and glutarimide K represents a severe competition, and (c) the product selectivity should be controlled by the amount of the isocyanates. In addition, it is demonstrated that there exist steric effects in the real substituted system, but missed in model system. Our calculations also show that although the results obtained on the model system could explain the mechanism in principle, the real substituted system could reflect the mechanism more exactly and make the reaction proceed with regioselectivity.     

A nanoscale dendrimer-based Fe24 cluster: synthesis and molecular self-assembly

We report the synthesis, characterisation and self-assembly of a nanoscopic Fe24 cluster using an organic dendrimer as a molecular substrate for building up well-defined molecular nanostructures.     

Suppressed electron hopping in a Au nanoparticle/H2S system: development towards a H2S nanosensor

We herein report and discuss electron transport within a Au/H2S nanoscale device and thereby highlight a phenomenon that may be used in the development of a novel on-chip H2S sensor.