New cyclic C-geranylflavanones isolated from Paulownia fortunei fruits with their anti-proliferative effects on three cancer cell lines.

Seven new C-geranylated flavanones, fortunones F - L (1-7), were isolated from the fresh mature fruits of Paulownia fortunei (Seem.) Hemsl. Their structures were determined by extensive spectroscopic data interpretation (UV, IR, HRMS, NMR, and CD). These new isolated compounds were all with a cyclic side chain modified from the geranyl group. Among them, compounds 1-3 all possessed a dicyclic geranyl modification, which was described firstly for Paulownia C-geranylated flavonoids. All the isolated compounds were subjected to the cytotoxic assay on human lung cancer cell A549, mouse prostate cancer cell RM1 and human bladder cancer cell T24, respectively. Results indicated A549 cell line was more sensitive to C-geranylated flavanones than the other two cancer cell lines and compounds 1, 7 and 8 exhibited potential anti-tumor effects (IC50 ˂ 10 µM). Further research revealed the effective C-geranylated flavanones could exert their anti-proliferative activity on A549 cells by inducing apoptosis and blocking cells in G1 phase.

Morphology-tunable WMoO nanowire catalysts for the extremely efficient elimination of tetracycline: kinetics, mechanisms and intermediates.

The presence of antibiotics in aquatic environments has attracted global concern. The Fenton system is one of the most popular methods for eliminating antibiotics in aquatic environments, but the existing Fenton system is limited due to the potential for secondary pollution, and the narrow pH range (∼3-5). In this study, we report that the bottlenecks for high-strength tetracycline (TC) wastewater treatment under neutral conditions can be tackled well by a class of mixed-valence W/Mo containing oxides (WMoO-x) with tunable morphologies. Triethanolamine was selected as a structure-directing agent to control the morphologies of the catalysts going from ultrathin nanowires (UTNWs) to wire-tangled nanoballs (WTNBs). As a proof of concept, the most efficient catalyst in the batch samples, WMoO-1 ultrathin nanowires, was employed as a model material for TC degradation, in which the coordinatively unsaturated metal atoms with oxygen defects serve as the sites for TC chemisorption and electron transfer. As a result, 91.75% of TC was degraded in 60 min for the initial TC concentration of 400 µM. Furthermore, LC-MS analysis confirmed that the TC could be degraded to nontoxic by-products without benzene rings, and finally mineralized to CO2 and H2O. ICP-MS and cycle experiments showed the good stability and reusability of WMoO-1 UTNWs in the Fenton-like system. The findings of this work provide fresh insights into the design of nanoscale catalyst morphology and reaffirm the versatility of doping in tuning catalyst activity, extending the range of the optimal pH values to neutral conditions. This is significant for the expansion of the heterogeneous Fenton-like family and its application in the field of water treatment.

Fluoride removal mechanism of bayerite/boehmite nanocomposites: roles of the surface hydroxyl groups and the nitrate anions.

Three-dimensional feather like bayerite/boehmite nanocomposites were synthesized by a facile one-pot hydrothermal method. The obtained nanocomposites were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The removal properties toward fluoride were investigated, including adsorption kinetics, adsorption isotherm, and influences of pH and coexisting anions. The maximal adsorption capacity was 56.80 mg g(-1) at pH 7.0, which is favorable compared to those reported in the literature using other adsorbents. The coexisting of sulfate and bicarbonate inhibited the fluoride removal especially at high concentrations. Furthermore, the removal mechanism was revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results suggest that both of the surface hydroxyl groups and the nitrate anions were participated in the ion-exchange process.

Parts per billion-level detection of benzene using SnO2/graphene nanocomposite composed of sub-6 nm SnO2 nanoparticles.

In the present work, the SnO(2)/graphene nanocomposite composed of 4-5 nm SnO(2) nanoparticles was synthesized using a simple wet chemical method for ppb-level detection of benzene. The formation mechanism of the nanocomposite was investigated systematically by means of simultaneous thermogravimetry analysis, X-ray diffraction, and X-ray photoelectron spectroscopy cooperated with transmission electron microscopy observations. The SnO(2)/graphene nanocomposite showed a very attractive improved sensitivity to toxic volatile organic compounds, especially to benzene, compared to a traditional SnO(2). The responses of the nanocomposite to benzene were a little higher than those to ethanol and the detection limit reached 5 ppb to benzene which is, to our best knowledge, far lower than those reported previously.

Metal oxide nanostructures and their gas sensing properties: a review.

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

Single-walled carbon nanotube/pyrenecyclodextrin nanohybrids for ultrahighly sensitive and selective detection of p-nitrophenol.

Electrochemical detection of p-nitrophenol (P-NP) using a highly sensitive and selective platform based on single-walled carbon nanotube/pyrenecyclodextrin (SWCNT/PyCD) nanohybrids is described for the first time. The electrochemical performance of the SWCNT/PyCD nanohybrid electrode was fully compared with bare glassy carbon, single-SWCNT, single-PyCD, and SWCNT/CD (without pyrene rings) electrodes. Besides the techniques of cyclic voltammetry and chronoamperometric transients, differential pulse voltammetry (DPV) has been used for the detection of P-NP without any interference from o-nitrophenol (O-NP) at the potentials of -0.80 and -0.67 V, respectively. The SWCNT/PyCD nanohybrid electrode is highly sensitive, and it shows an ultrahigh sensitivity of 18.7 µA/µM toward P-NP in contrast to the values reported previously. The detection limit (S/N = 3) of the SWCNT/PyCD nanohybrid electrode toward P-NP is 0.00086 µM (0.12 ppb), which is well below the allowed limit in drinking water, 0.43 µM, given by the U.S. Environmental Protection Agency (EPA). The analytical performance of the SWCNT/PyCD nanohybrid electrode toward P-NP is superior to the existing electrodes.

Electrochemical impedance determination of polychlorinated biphenyl using a pyrenecyclodextrin-decorated single-walled carbon nanotube hybrid.

This work reports the first detailed study on an electrochemical impedance sensor for determination of polychlorinated biphenyl (PCB), such as 3,3',4,4'-tetrachlorobiphenyl (PCB-77), based on a single-walled carbon nanotube/pyrenecyclodextrin (SWCNT/PyCD) hybrid.

Stripping voltammetric detection of mercury(II) based on a surface ion imprinting strategy in electropolymerized microporous poly(2-mercaptobenzothiazole) films modified glassy carbon electrode.

This work reports a surface ion imprinting strategy in electropolymerized microporous poly(2-mercaptobenzothiazole) (MPMBT) films at the surface of glassy carbon electrode (GCE) for the electrochemical detection of Hg(II). The Hg(II)-imprinted MPMBT/GCE exhibits larger binding to functionalized capacity, faster binding kinetics and higher selectivity to template Hg(II) due to their high ratio of surface-imprinted sites, larger surface-to-volume ratios, the complete removal of Hg(II) templates and larger affinity to Hg(II). The square wave anodic stripping voltammetry (SW ASV) response of the Hg(II)-imprinted MPMBT/GCE to Hg(II) is ca. 3.0 and 5.9 times larger than that at the direct imprinted poly(2-mercaptobenzothiazole) modified GCE and non-imprinted MPMBT/GCE sensor, respectively; and the detection limit for Hg(II) is 0.1nM (which is well below the guideline value given by the World Health Organization). Excellent wide linear range (1.0-160.0nM) and good repeatability (relative standard deviation of 2.5%) were obtained for Hg(II). The interference experiments showed that mercury signal was not interfered in the presence of Pb(II), Cd(II), Zn(II), Cu(II) and Ag(I), respectively. These values, particularly the high sensitivity and excellent selectivity compared favorably with previously reported methods in the area of electrochemical Hg(II) detection, demonstrate the feasibility of using the prepared Hg(II)-imprinted MPMBT/GCE for efficient determination of Hg(II) in aqueous environmental samples.