Polyethyleneimine-capped silver nanoclusters as a fluorescence probe for sensitive detection of hydrogen peroxide and glucose

In this work, we utilized polyethyleneimine-capped silver nanoclusters (PEI-Ag nanoclusters) to develop a new fluorometric method for the determination of hydrogen peroxide and glucose with high sensitivity. The PEI-Ag nanoclusters have an average size of 2 nm and show a blue emission at 455 nm. The photostable properties of the PEI-Ag nanoclusters were examined. The fluorescence of the PEI-Ag nanoclusters could be particularly quenched by H₂O₂. The oxidization of glucose by glucose oxidase coupled with the fluorescence quenching of PEI-Ag nanoclusters by H₂O₂ can be used to detect glucose. Under optimum conditions, the fluorescence intensity quenched linearly in the range of 500 nM–100 μM with high sensitivity. The detection limit for H₂O₂ was 400 nM. And a linear correlation was established between fluorescence intensity (F₀ − F) and concentration of glucose in the range of 1.0 × 10⁻⁶ to 1.0 × 10⁻⁵ M and 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M with a detection limit of 8.0 × 10⁻⁷ M. The method was used for the detection of glucose in human serum samples with satisfactory results. Furthermore, the mechanism of sensitive fluorescence quenching response of Ag nanoclusters to glucose and H₂O₂ has been discussed.     

First total synthesis of four natural prenylated flavonoids

A facile approach for the first total synthesis of prenylated flavonoids,(±)-abyssinone-Vl-4-O-methyl ether 1,(±)-abyssinoneIV -4’-O-methyl ether 2,(±)-abyssinone-V-4’-O-methyl ether 3 and(±)-sigmoidin E 4 has been described.The key intermediate 4-hydroxy-3,5-di-(3-methylbut-2-enyl)benzaldehyde 6 was also first synthesized that features regioselective prenylation of 4-hydroxybenzaldehyde and crystallizing with petroleum ether from the reaction mixture by freeze-out effect.     

Cytotoxic terpenes from Abies sibirica

One new and 16 known compounds were isolated from Abies sibirica.Their structures were assigned mainly on the basis of NMR and MS spectroscopic data.In bioassay for anti-proliferative activity against four human tumor cells,compound 7 exhibited selective anti-proliferative activity against COLO-205 tumor cell with an IC₅₀ value of 0.9μg/mL.     

A light-through-side cell and co-used furnace designed for micro-Raman spectra study on volatile melts

A new type of sample cell specially designed for micro-Raman spectra study on volatile melts is described.The cell is made of quartz.The lower section of the cell is circular ring-shaped and the one-end-closed hole in the cell is used for locating the heating body.The tube attached to the cell lid for placing the thermal couple is inserted into the sample,which ensures that the temperature measurement accuracy is good.The cell can be sealed for reducing the effect of the composition change caused by the inhomogeneous volatilization.During the Raman spectra scanning,the laser beam is transmitted into the cell through the side but not the top.Meanwhile,a furnace has been designed to match the cell.The heating body is closely coupled with the sample cell, and there is a hole on the side wall of the furnace for the entrance of the microlens.The assembly has performed well in the tested Raman spectrum measurement of molten NaNO₃ at 602℃.     

Rare‐Earth Nanoparticles with Enhanced Upconversion Emission and Suppressed Rare‐Earth‐Ion Leakage

Upconversion emissions from rare‐earth nanoparticles have attracted much interest as potential biolabels, for which small particle size and high emission intensity are both desired. Herein we report a facile way to achieve NaYF₄:Yb,Er@CaF₂ nanoparticles (NPs) with a small size (10–13 nm) and highly enhanced (ca. 300 times) upconversion emission compared with the pristine NPs. The CaF₂ shell protects the rare‐earth ions from leaking, when the nanoparticles are exposed to buffer solution, and ensures biological safety for the potential bioprobe applications. With the upconversion emission from NaYF₄:Yb,Er@CaF₂ NPs, HeLa cells were imaged with low background interference.     

One‐Step Synthesis of SnO2 and TiO2 Hollow Nanostructures with Various Shapes and Their Enhanced Lithium Storage Properties

A versatile one‐step method for the general synthesis of metal oxide hollow nanostructures is demonstrated. This method involves the controlled deposition of metal oxides on shaped α‐Fe₂O₃ crystals which are simultaneously dissolved. A variety of uniform SnO₂ hollow nanostructures, such as nanococoons, nanoboxes, hollow nanorings, and nanospheres, can be readily generated. The method is also applicable to the synthesis of shaped TiO₂ hollow nanostructures. As a demonstration of the potential applications of these hollow nanostructures, the lithium storage capability of SnO₂ hollow structures is investigated. The results show that such derived SnO₂ hollow structures exhibit stable capacity retention of 600–700 mAh g^?1 for 50 cycles at a 0.2 C rate and good rate capability at 0.5–1 C, perhaps benefiting from the unique structural characteristics.     

Two heptadentate Co(III) and Mn(III) complexes with partially deprotonated cyclen derivative bearing four hydroxypropyl pendants: structure,DNA binding and DNA cleavage

Two new complexes, (Co^III)₂(H₃L^?)₂(0.5H₂O)₂(ClO₄)₄ (I) and (Mn^III)₂(H₃L^?)₂(0.5H₂O)₂ (ClO₄)₄ (II), were synthesized and crystallographically characterized [H₄L = 1,4,7,10‐tetra‐(2‐hydroxypropyl)‐l,4,7,10‐tetraazacyclododecane] using electrospray ionization mass spectrometry and X‐ray photoelectron spectrometery. The characterizations confirmed that the valences of the metal ions increased from divalent to trivalent due to deprotonation of one OH group (H₄L was in the form of H₃L^?). Owing to the instability of Co(III) and Mn(III) in both air and in solution, they preferred to exist in divalent form. The two heptadentate complexes are extraordinary in that the chiral pendants of the complexes are different in configuration. Spectroscopic studies, viscosity measurements, thermal denaturation experiments and circular dichroism spectra demonstrated that the complexes were prone to interact with DNA by groove binding. At micromolar concentrations and under physiological conditions, the two complexes were able to oxidatively cleave the supercoiled pUC19 plasmid DNA into its nicked and linear forms. Mechanistic studies using various additives suggest the complexes had structures different from those of other inorganic complexes. These are the first reported inorganic complexes not containing planar aromatic ligands and yet binding at the major groove. Copyright © 2012 John Wiley & Sons, Ltd.     

Spiro‐Configured Bipolar Host Materials for Highly Efficient Electrophosphorescent Devices

In this study, we synthesized and characterized a series of spirobifluorene‐based bipolar compounds (D2 ACN, DNPACN, DNTACN, and DCzACN) in which a dicyano‐substituted biphenyl branch, linked orthogonally to a donor biphenyl branch bearing various diarylamines, acted as an acceptor unit allowing fine‐tuning of the morphological stability, triplet energy, bipolar transport behavior, and the HOMO and LUMO energy levels. The promising physical properties of these new compounds, together with their ability to transport electrons and holes with balanced mobilities, made them suitable for use as host materials in highly efficient phosphorescent organic light‐emitting diodes (PhOLEDs) with green iridium‐based‐ or red osmium‐based phosphors as the emitting layer (EML). We adopted a multilayer structure to efficiently confine holes and electrons within the EML, thus preventing exciton diffusion and improving device efficiency. The device incorporating D2 ACN doped with the red emitter [Os(bpftz)₂(PPhMe₂)₂] (bpftz=3‐(trifluoromethyl)‐5‐(4‐tert‐butylpyridyl)‐1,2,4‐triazolate) gave a saturated red electrophosphorescence with CIE coordinates of (0.65, 0.35) and remarkably high efficiencies of 20.3 % (21 cd A^?1) and 13.5 Lm W^?1 at a practical brightness of 1000 cd m^?2.