Trace detection of nitro aromatic explosives by highly fluorescent g-C3N4 nanosheets.

Highly fluorescent g-C3N4 nanosheets were facilely fabricated by exfoliating bulk g-C3N4 under ultrasonic irradiation for 1 h. The atomic force microscopy (AFM) image shows that the resultant g-C3N4 nanosheets are ∼6-14 nm thick, and the suspension is stable in air for several weeks. Remarkably, the obtained nanosheets exhibited strong fluorescence with an extremely high quantum yield (QY) up to 32%, and high sensitivity, selectivity, as well as a fast response to nitro aromatic explosives were observed. Typically, the quenching efficiency coefficient Ksv for PNP was 30,460 M(-1), which proved that the resultant nanosheets possessed an extremely high sensitivity for nitro-phenol PNP detection.

Fabrication of magnetically separable fluorescent terbium-based MOF nanospheres for highly selective trace-level detection of TNT.

In this work, we present novel kinds of Fe3O4@Tb-BTC magnetic metal-organic framework (MOF) nanospheres which possess both magnetic characteristics and fluorescent properties using a layer by layer assembly technique. The structure and morphology of the as-prepared Fe3O4@Tb-BTC were systematically characterized and it was applied in detection of nitroaromatic explosives, such as 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), 2-nitrotoluene (2-NT), 4-nitrotoluene (4-NT), nitrobenzene (NB) and picric acid (PA). The results indicate that the fluorescence intensity of Fe3O4@Tb-BTC can be quenched by all analytes studied in the present work. Remarkably, the as-synthesized nanospheres exhibit high sensitivity for 2,4,6-trinitrotoluene (TNT) detection with Ksv value of (94 800 M(-1)). Besides, the magnetic nanospheres can be easily recycled, which makes it more convenient for reutilization and friendly to the environment. The results show that it has broad application prospects in the detection of nitroaromatic explosives.

Metal-organic frameworks MIL-88A hexagonal microrods as a new photocatalyst for efficient decolorization of methylene blue dye.

Metal-organic frameworks (MOFs) MIL-88A hexagonal microrods as a new photocatalyst show an active performance for methylene blue (MB) dye decolorization using visible light. MB decolorization over the MIL-88A photocatalyst follows first-order kinetics. The addition of a H2O2 electron acceptor can markedly enhance the photocatalytic MB decoloration performance of MIL-88A. Moreover, MIL-88A showed a very stable activity for MB decoloration after four consecutive usages. Owing to the advantages of the visible light response, low cost and abundance in nature, this active MIL-88A MOF photocatalyst would have great potential for environmental purification.

Fe3O4@MOF core-shell magnetic microspheres as excellent catalysts for the Claisen-Schmidt condensation reaction.

Separation and recycling of catalysts after catalytic reactions are critically required to reduce the cost of catalysts as well as to avoid the generation of waste in industrial applications. In this work, we present a facile fabrication and characterization of a novel type of MOF-based porous catalyst, namely, Fe3O4@MIL-100(Fe) core-shell magnetic microspheres. It has been shown that these catalysts not only exhibit high catalytic activities for the Claisen-Schmidt condensation reactions under environmentally friendly conditions, but remarkably, they can be easily separated and recycled without significant loss of catalytic efficiency after being used for many times. Therefore, compared to other reported catalysts used in the Claisen-Schmidt condensation reactions, these catalysts are green, cheap and more suitable for large scale industrial applications.

One-pot synthesis of metal-organic framework@SiO2 core-shell nanoparticles with enhanced visible-light photoactivity.

This paper presents a novel strategy to prepare Cu3(BTC)2@SiO2 core-shell nanoparticles in the size range of 200-400 nm using a new one-pot strategy under ultrasonic irradiation at room temperature. In this approach, the silica shell thickness could be finely tuned in the size range of 12-60 nm for various reaction times. Nanocomposite thin films were fabricated on the glass substrates by Sol-Gel spin coating using the products for 1.5 h, 2 h and 2.5 h, respectively, and heat treated using an infrared lamp heating system in air. The photocatalytic degradation of phenol in aqueous solution using Cu2(BTC)3@SiO2 thin films was investigated under visible light irradiation at pH 4. After a 45 min reaction with phenol, the degradation rate was up to 93.1%. Moreover, the thin film photocatalysts could be reused 5 times without appreciable loss of photocatalytic activity for degradation of phenol. The present work clearly shows that the films as photocatalysts showed higher photocatalytic performance.

Controlled synthesis of novel Au@MIL-100(Fe) core-shell nanoparticles with enhanced catalytic performance.

A novel porous Au@MIL-100(Fe) core-shell nanocatalyst with controllable MIL-100(Fe) shell thickness has been fabricated by using a versatile step-by-step fashion. Catalytic studies show that the Au@MIL-100(Fe) nanocatalyst exhibits much higher catalytic activity than the pure Au nanoparticles, suggesting that the MIL-100(Fe) shell enhances the catalytic activity via a synergistic effect.

Microwave-assisted synthesis of highly fluorescent nanoparticles of a melamine-based porous covalent organic framework for trace-level detection of nitroaromatic explosives.

Covalent organic frameworks (COFs) are a new generation of porous materials constructed from light elements linked by strong covalent bonds. Herein we present rapid preparation of highly fluorescent nanoparticles of a new type of COF, i.e. melamine-based porous polymeric network SNW-1, by a microwave-assisted synthesis route. Although the synthesis of SNW-1 has to be carried out at 180°C for 3d under conventional reflux conditions, SNW-1 nanoparticles could be obtained in 6h by using such a microwave-assisted method. The results obtained have clearly demonstrated that microwave-assisted synthesis is a simple yet highly efficient approach to nanoscale COFs or other porous polymeric materials. Remarkably, the as-synthesized SNW-1 nanoparticles exhibit extremely high sensitivity and selectivity, as well as fast response to nitroaromatic explosives such as 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (Tetryl) and picric acid (PA) without interference by common organic solvents, which is due to the nanoscaled size and unique hierarchical porosity of such fluorescence-based sensing material.

Fabrication of composite photocatalyst g-C3N4-ZnO and enhancement of photocatalytic activity under visible light.

The g-C(3)N(4)-ZnO composite photocatalysts with various weight percents of ZnO were synthsized by a simple calcination process. The photocatalysts were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), UV-vis diffuse reflection spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The PXRD and HR-TEM results show that the composite materials consist of hexagonal wurzite phase ZnO and g-C(3)N(4). The solid-state UV-vis diffuse reflection spectra show that the absorption edge of the composite materials shifts toward the lower energy region and to longer wavelengths in comparison with pure ZnO and g-C(3)N(4). Remarkably, the photocatalytic activity of g-C(3)N(4)-ZnO composites has been demonstrated, via photodegradation of Methyl Orange (MO) and p-nitrophenol experiments. The photocatalytic activity of g-C(3)N(4)-ZnO for photodegradation of Methyl Orange and p-nitrophenol under visible light irradiation was increased by over 3 and 6 times, respectively, to be much higher than that of single-phase g-C(3)N(4), clearly demonstrating a synergistic effect between ZnO and g-C(3)N(4). The concentrations of Zn(2+) in g-C(3)N(4)-ZnO system after a photocatalytic reaction at various reaction times were found to be much lower than those for a ZnO system under the same reaction conditions, indicating that the g-C(3)N(4)-ZnO composite possesses excellent long-term stability for a photocatalytic reaction in aqueous solutions. Furthermore, a synergistic photocatalysis mechanism between ZnO and g-C(3)N(4) was proposed based on the photodegradation results. Such obviously improved performance of g-C(3)N(4)-ZnO can be ascribed mainly to the enhancement of electron-hole separations at the interface of ZnO and g-C(3)N(4).

A rational self-sacrificing template route to metal-organic framework nanotubes and reversible vapor-phase detection of nitroaromatic explosives.

Metal-organic framework nanotubes (MOFNTs) are achieved by a strategy in which MOF nanorods formed initially act as a self-sacrificing template for the formation of the final MOFNTs. The fluorescent MOFNTs obtained exhibit high sensitivity, significant selectivity, and a fast response rate for the reversible vapor-phase detection of nitroaromatic explosives.

Thiol-functionalization of metal-organic framework by a facile coordination-based postsynthetic strategy and enhanced removal of Hg2+ from water.

The presence of coordinatively unsaturated metal centers in metal-organic frameworks (MOFs) provides an accessible way to selectively functionalize MOFs through coordination bonds. In this work, we describe thiol-functionalization of MOFs by choosing a well known three-dimensional (3D) Cu-based MOF, i.e. [Cu(3)(BTC)(2)(H(2)O)(3)](n) (HKUST-1, BTC=benzene-1,3,5-tricarboxylate), by a facile coordination-based postsynthetic strategy, and demonstrate their application for removal of heavy metal ion from water. A series of [Cu(3)(BTC)(2)](n) samples stoichiometrically decorated with thiol groups has been prepared through coordination bonding of coordinatively unsaturated metal centers in HKUST-1 with -SH group in dithioglycol. The obtained thiol-functionalized samples were characterized by powder X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, infrared spectroscopy, and N(2) sorption-desorption isothermal. Significantly, the thiol-functionalized [Cu(3)(BTC)(2)](n) exhibited remarkably high adsorption affinity (K(d)=4.73 × 10(5)mL g(-1)) and high adsorption capacity (714.29 mg g(-1)) for Hg(2+) adsorption from water, while the unfunctionalized HKUST-1 showed no adsorption of Hg(2+) under the same condition.

New photocatalysts based on MIL-53 metal-organic frameworks for the decolorization of methylene blue dye.

The photocatalytic decolorization of methylene blue dye in aqueous solution using a novel photocatalyst MIL-53(Fe) metal-organic frameworks was investigated under UV-vis light and visible light irradiation. The effect of electron acceptor H(2)O(2), KBrO(3) and (NH(4))(2)S(2)O(8) addition on the photocatalytic performance of MIL-53(Fe) was also evaluated. The results show that MIL-53(Fe) photocatalyst exhibited photocatalytic activity for MB decolorization both under UV-vis light and visible light irradiation, and the MB decolorization over MIL-53(Fe) photocatalyst followed the first-order kinetics. The addition of different electron acceptors all enhances the photocatalytic performance of MIL-53(Fe) photocatalyst, and the enhanced rate follows the order of H(2)O(2)>(NH(4))(2)S(2)O(8)>KBrO(3) under UV-vis light irradiation, while in the order of (NH(4))(2)S(2)O(8)>H(2)O(2)>KBrO(3) under visible light irradiation. Moreover, MIL-53(Fe) did not exhibit any obvious loss of the activity for MB decolorization during five repeated usages. The photocatalytic activities over MIL-53(M) (M=Al, Fe), the isostructure to MIL-53(Fe), indicate that the metal centers show nil effect on the photocatalytic activity of MIL-53(M) photocatalysts.

Microwave-enhanced synthesis of magnetic porous covalent triazine-based framework composites for fast separation of organic dye from aqueous solution.

A novel type of magnetic porous carbonaceous polymeric material, CTF/Fe(2)O(3) composite (CTF = covalent triazine-based framework), has been synthesized by a facile microwave-enhanced high-temperature ionothermal method. By selecting ZnCl(2) as a reaction medium and the Lewis acid catalyst, and choosing FeCl(3)·6H(2)O as an iron oxide precursor, a series of CTF/Fe(2)O(3) composites with different γ-Fe(2)O(3) contents has been prepared in 60 min. The resulting samples were characterized by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibration sample magnetometer (VSM), and N(2) sorption-desorption isotherms. The obtained CTF/Fe(2)O(3) composites exhibit high surface areas (930-1149 m(2) g(-1)), and their saturation magnetizations at 300 K vary from 1.1 to 5.9 emu g(-1), depending respectively on different Fe(2)O(3) contents (6.43-12.43 wt%) in the CTF/Fe(2)O(3) composites. The CTF/Fe(2)O(3) composites were applied to remove organic dye from aqueous solution by selecting methyl orange as a model molecule, and both high adsorption capacity (291 mg g(-1), corresponding to 0.889 mmol g(-1)) and fast adsorption kinetics (k(ads) = 4.31 m(2) mg(-1) min(-1)) were observed.

Facile synthesis of nanocrystals of a microporous metal-organic framework by an ultrasonic method and selective sensing of organoamines.

In this work we present the rapid synthesis of nanocrystals of a fluorescent microporous metal-organic framework using an ultrasonic method, and their utility for selective sensing of organoamines.

Hydrolysis of p-nitrophenyl picolinate catalyzed by metal complexes of N-alkyl-3,5-bis(hydroxymethyl)-1,2,4-triazole in CTAB micelles.

Two lipophilic ligands containing triazole and hydroxyl groups, N-alkyl(C(n)H(2n+1))-3,5-bis(hydroxymethyl)-1,2,4-triazole (n=10 and 12), were synthesized. Effects of their Cu(II) and Ni(II) complexes on the hydrolysis of p-nitrophenyl picolinate (PNPP) in cetyltrimethylammonium bromide (CTAB) micelles have been investigated kinetically, and some kinetic parameters of the reactions were obtained by employing the ternary complex kinetic model for metallomicellar catalysis. It was found that Cu(II) complexes of these triazole-based ligands showed more effective catalytic activity on the hydrolysis of PNPP than Ni(II) complexes. Also, the apparent first-order rate constants for product formation in the metallomicellar phase (k(N)(')), the association constants between the substrate and the binary complex (K(T)), and the association constants between the metal ion and the ligand (K(M)) increased with an increase in pH value, which may be attributed to an increase in the nucleophilicity of the hydroxyl groups in the ligand or the electrophilicity of the substrate at higher pH. In addition, at constant pH, k(N)(') and K(T) increased with an increase in the hydrocarbon chain length of the ligand, while K(M) decreased.

Study on the viscosity of cationic gemini surfactant-nonionic polymer complex in water.

Interactions between a cationic gemini surfactant, 1,2-ethane bis(dimethyldodecylammonium bromide) (designated as 12-2-12), and a nonionic polymer polyvinyl alcohol (PVA) were investigated by means of viscosity and specific conductance. Results show that PVA displays special viscosity behavior in aqueous solutions containing the gemini surfactant 12-2-12, which is due to the molecular interaction of the polymer and the surfactant. It was found that the special viscosity depended on ionization of the surfactant, as well as polymer concentration and surfactant concentration in the nonionic polymer-surfactant system. A theoretical expression for the dependence of the solution viscosity on the ionization of the surfactant micelle was given, and the new equation proved to be in good agreement with the experimental data.