Magnetically separable Pd-iron-oxides composites as highly efficient and recyclable catalysts for ultra-rapid degradation and debromination of polybrominated diphenyl ethers.

When precious nano-metals are used as environmental catalysts, it is important to tune the particle sizes and the reusability of the nano-metals for achieving their highly efficient catalytic performance at a low cost. In the present work, magnetic iron oxides (FeOx-Y) nanoparticles were pre-prepared as supports of nano-metals, where Y represented the mole percentage of Fe(III) in the total iron (Y ≥ 50 %). FeOx-Y (support), PdCl42- (Pd source) and NaBH4 (reducing agent) were added into the organic pollutant solution containing 2,2',4,4'-tetrabromodiphenyl ether (BDE47). After the NaBH4 was added, the followed reaction realized not only the rapid in-situ preparation of a Pd-loaded FeOx-Y composite catalyst (Pd-FeOx-Y), but also the ultra-fast and complete debromination of BDE47 within 30 s. Comparing the case without adding FeOx-Y, the debromination efficiency of BDE47 was much promoted in the presence of FeOx-Y. The support-induced enhancing effect on the catalytic ability of Pd nanoparticles was improved by increasing the Fe(III) content in the support, being attributed to the much more hydroxyl groups on the support surface. Considering both the catalytic and recovery abilities of Pd-FeOx-Y, Pd-FeOx-75 was the optimal choice because it could be magnetically recovered and re-used for multiple cycles with high catalytic activities. The presently developed "catalyst preparation-pollutant degradation" one-pot system could be applied to conduct complete debromination of all the PBDEs.

A functional Au array SERS chip for the fast inspection of pesticides in conjunction with surface extraction and coordination transferring.

The fast inspection of the pesticide residues on fruits and vegetables requires the development of facile, sensitive and accurate methods. Surface enhanced Raman scattering (SERS) is a promising way to provide a fast inspection method, which requires significant improvements in the reproducibility and feasibility. In the present work, an SERS method was developed for the fast inspection of pesticides on fruit peels in conjunction with surface extraction and coordination transferring. In this new method, the residual pesticides were directly extracted from fruit peels with an appropriate extraction solution and then quantitatively transferred onto an organic solvent-compatible Au array SERS chip through the strong chemical interactions between the heteroatoms in the pesticides and the gold surface. The functional SERS chip was fabricated by the interfacial assembly of an Au array on a membrane, which produced dense and uniformly distributed SERS hot spots and enabled compatibility with random curvature surfaces and handheld Raman spectrometers. As a proof of concept, sulfur atoms containing thiram on apples were detected at a concentration as low as 5 ng cm-2 with good reproducibility (relative standard deviation lower than 10%). The strong interactions between the sulfur atoms and gold surface during the coordination transferring process were confirmed by the enhanced vibrations of the specified bands occurring in both the Raman and IR spectra. This surface extraction-coordination transferring-based method holds wide applicability for heteroatom-containing pesticides, as demonstrated by the detection of various S- and P-containing pesticides.

Ultrarapid and Deep Debromination of Tetrabromodiphenyl Ether over Noble-Metal-Free Cu/TiO2 Nanocomposites under Mild Conditions.

Fast and deep debromination of polybrominated diphenyl ethers (PBDEs) under mild conditions is a challenge in the field of pollution control. A strategy was developed to achieve it by exploiting Cu/TiO2 composites as a noble-metal-free catalyst. Toward the debromination of 2,2',4,4'-tetrabromodiphenyl ether (BDE47) as a typical PBDE, the use of Cu/TiO2 as a catalyst and hydrazine hydrate (N2H4·H2O) as a reducing agent yielded a degradation removal of 100% and a debromination efficiency of 87.7% in 3 s. A complete debromination of BDE47 at 1500 mg L-1 was possible by successively adding N2H4·H2O. A debromination pathway involving active H atom species was proposed for the catalytic transfer hydrogenation (CTH) of PBDEs according to the identified degradation intermediates. A mechanism was further clarified by density functional theory calculations: electrons are delivered from N2H4·H2O to the metallic Cu atom via a coordination of N in N2H4·H2O with Cu atoms. The electron-trapped Cu atom interacts with adsorbed BDE47 to form a transition complex, and then the debromination of this complex occurs on the surface of Cu nanoparticles due to the hydrogen donation of N2H4·H2O through the CTH process. The new method provides a highly efficient method to remove brominated pollutants.

A surface-enhanced Raman scattering method for detection of trace glutathione on the basis of immobilized silver nanoparticles and crystal violet probe.

Unsatisfactory sensitivity and stability for molecules with low polarizability is still a problem limiting the practical applications of surface-enhanced Raman scattering (SERS) technique. By preparing immobilized silver nanoparticles (Fe3O4/Ag) through depositing silver on the surface of magnetite particles, a highly sensitive and selective SERS method for the detection of trace glutathione (GSH) was proposed on the basis of a system of Fe3O4/Ag nanoparticles and crystal violet (CV), in which the target GSH competed with the CV probe for the adsorption on the Fe3O4/Ag nanoparticles. Raman insensitive GSH replaced the highly Raman sensitive CV adsorbed on the surface of Fe3O4/Ag particles. This replacement led to a strong decrease of the CV SERS signal, which was used to determine the concentration of GSH. Under optimal conditions, a linear response was established between the intensity decrease of the CV SERS signal and the GSH concentration in the range of 50-700 nmol L(-1) with a detection limit of 40 nmol L(-1). The use of a Fe3O4/Ag substrate provided not only a great SERS enhancement but also a good stability, which guarantees the reproducibility of the proposed method. Its use for the determination of GSH in practical blood samples and cell extract yielded satisfactory results.

Efficient oxidative debromination of decabromodiphenyl ether by TiO2-mediated photocatalysis in aqueous environment.

Direct evidence was first demonstrated for the oxidative degradation of decabromodiphenyl ether (BDE209) in aqueous TiO(2) dispersions under UV irradiation (λ > 340 nm). BDE209 was hardly debrominated over TiO(2) in UV-irradiated acetonitrile dispersions, but the addition of water into the dispersions greatly enhanced its photocatalytic oxidative debromination. The debromination efficiency of BDE209 as high as 95.6% was achieved in aqueous TiO(2) dispersions after 12 h of UV irradiation. The photocatalytic oxidation of BDE209 resulted in generation of aromatic ring-opening intermediates such as brominated dienoic acids, which were further degraded by prolonging UV irradiation time. The photocatalytic oxidative debromination of BDE209 was further confirmed by the observation that the BDE209 degradation in water-acetonitrile mixtures with different water contents was positively correlated with the formation of •OH radicals, but not photogenerated electrons. The use of water not only avoided the scavenging of reactive radicals by organic solvent but also enhanced the adsorption of BDE209 on the surface of TiO(2), both of which favor the contact of BDE209 with photogenerated holes and •OH species. The confirmation of efficient oxidative degradation and debromination of BDE209 is very important for finding new ways to remove polybrominated diphenyl ethers from the environment.

Removing organic contaminants with bifunctional iron modified rectorite as efficient adsorbent and visible light photo-Fenton catalyst.

Iron-modified rectorite (FeR) was prepared as both adsorbent and catalyst. The iron modification increased layer-to-layer spacing and surface area of rectorite, leading to much increased adsorption of Rhodamine B (RhB) on rectorite. The maximum adsorption capacity of RhB on FeR reached 101mgg(-1) at pH 4.5, being 11 folds of that on the unmodified one. The iron modification also enabled rectorite to have efficient visible light photocatalytic ability. The apparent rate constant for the degradation of RhB (80µM) at 298K and pH 4.5 in the presence of H(2)O(2) (6.0mM) and FeR (0.4gL(-1)) was evaluated to be 0.0413min(-1) under visible light and 0.122min(-1) under sunlight, respectively. The analysis with electron spin resonance spin-trapping technique supported that the iron modified rectorite effectively catalyzed the decomposition of H(2)O(2) into hydroxyl radicals. On the basis of the characterization and analysis, the new bifunctional material was well clarified as both adsorbent and photocatalyst in the removing of organic pollutants.

Sono-assisted preparation of magnetic magnesium-aluminum layered double hydroxides and their application for removing fluoride.

A simple ultrasound-assisted co-precipitation method in combination with a calcination treatment was developed to prepare magnetic Mg-Al layered double hydroxides composite as an adsorbent material to remove fluoride ions from aqueous solutions. The application of ultrasound in the preparation process promoted the formation of the hydrotalcite-like phase and drastically shortened the time being required for preparation of the crystalline composite. It was found that the ultrasound irradiation assistance decreased the size of the composite particles and increased the specific surface area, being favorable to the improvement of the adsorption capacity. The composite prepared under the ultrasound irradiation exhibited fairly high maximum adsorption capacity of fluoride (47.7 mg g(-1)), which was 60% higher than that of the composite prepared without the ultrasound irradiation assistance with the same aging time. The thermodynamic and kinetic studies demonstrated that the adsorption of fluoride ions involved the reconstruction of the layered structure in the composite. In addition, the magnetic composite can be effectively and simply separated by using an external magnetic field, and then regenerated by desorption and calcination.

A simple fluorescent probe for the determination of dissolved oxygen based on the catalytic activation of oxygen by iron(II) chelates.

This work aims at establishing a simple fluorescent probe for the determination of dissolved oxygen. It is found that iron(II) ions activate oxygen to produce reactive species being capable of oxidizing non-fluorescent coumarin to fluorescent 7-hydroxycoumarin. However, this process is not effective because the yield of the reactive species is very low in the presence of simple iron(II) salts alone. The addition of organic ligands such as oxalate results in the formation of complexes between iron(II) ions, which leads to considerable increase in the yield of reactive species (such as hydroxyl radicals) and then increase in the fluorescence intensity of 7-hydroxycoumarin to a significant level. It has been observed that in the mixture solution of iron(II) ions, ligand, coumarin, and dissolved oxygen, there is an excellent linear response between the fluorescence and dissolved oxygen. Therefore, a new spectrofluorimetric method has been proposed for the determination of dissolved oxygen by using catalytic activation of O(2) by iron(II) chelates. Under optimized conditions, a linear correlation (r=0.995) has been observed between the fluorescence intensity of 7-hydroxycoumarin at 456 nm and the concentration of dissolved oxygen over the range of 0.96-9.22 mg L(-1). The limit of detection for dissolved oxygen at a signal-to-noise ratio of 3 has been estimated to be 0.35 mg L(-1). The proposed method has been applied to determine the concentration of dissolved oxygen in practical water samples with results as satisfactory as that obtained by the standard iodometric method.

[Effect of propofol on spinal cord apoptosis associated with aortic cross-clamping in rabbits].

OBJECTIVE: To investigate the effect and mechanism of propofol on the spinal cord apoptosis associated with aortic cross-clamping in rabbits. METHODS: Twenty-four rabbits were randomly divided into sham operation group (A), ischemia/reperfusion group (B) and propofol group (C). In group B and C, the infrarenal aorta was clamped for 40 minutes followed by 7 days reperfusion. Ten minutes before clamping, group C was given propofol 5 mg/kg intravenously and continued at a rate of 20 mg x kg(-1)x h(-1) until unclamping. The aorta was not clamped in group A. The plasma concentrations of malondialdehyde (MDA) and superoxide dismutase (SOD) were determined at 10 minutes before clamping (C-10), before unclamping (C40), at 60 minutes (R60) and on the 7th day (R7 d) unclamping. Apoptotic spinal cord cells and expressions of Bax, Bcl-2 protein were measured by immunohistochemical technique. RESULTS: (1)The concentrations of MDA after ischemia and reperfusion in group B were increased significantly compared with C-10 and those in group A (P<0.05 or P<0.01), which in group C were significantly lower than those in group B (P<0.05), but not in group A. Changes in SOD activity were opposite to those in MDA contents in various groups. (2)The expressions of Bax protein in group B were significantly increased compared with those in group A (P<0.05), while the expression of Bcl-2 protein decreased. In group C, Bax protein expression was markedly lower than those in group B and higher than those in group A (P<0.01 and P<0.05), the expression of Bcl-2 was higher than those in groups B and A (both P<0.01). (3)The number of apoptosis cells in group B was much higher than that in group A, which in group C was much lower than that in group B, but higher than that in group A. (4)The ratio of paralysis in group C was significantly lower than that in group B with a high neurologic score (both P<0.01). CONCLUSION: Propofol can reduce the spinal cord apoptosis associated with aortic cross-clamping in rabbits. The possible mechanism is related to the effect of decreasing Bax expression, increasing Bcl-2 expression, and enhancing antioxidation.

Ring-opening iodo- and bromosilation of lactones for the formation of silyl haloalkanoates.

Ring-opening halosilation of lactones with two types of reagents, Et(3)SiH/MeI(PdCl(2)) (1a) and Et(3)SiH/AllylBr(PdCl(2)) (1b), was studied. Cyclic esters such as gamma-butyrolactones, delta-valerolactone, and 6-hexanolide reacted with 1 equiv of 1a,b to give triethylsilyl omega-iodo- and omega-bromoalkanoates in good yields. Reaction of an acyclic ester, methyl benzoate, with 1a afforded triethylsilyl benzoate. O-Silyl-protected amino acids could be obtained by amination of the halosilation products, triethylsilyl omega-bromoalkanoates.