Plasmon-assisted degradation of methylene blue with Ag/AgCl/montmorillonite nanocomposite under visible light.

Metal-semiconductor compounds, such as Ag/AgX (X=Cl, Br, I), enable visible light absorption and separation of photogenerated electron-hole through surface plasmon resonance (SPR) effect. However, the electron-hole generated and separated by light are vulnerable in Ag/AgX phase because of the occurrence of secondary recombined. In order to more effectively utilize the SPR photocatalytic effect, nanoparticles are located in a matrix. In this article, Ag/AgCl nanoparticles were synthesized in montmorillonite (MMT) matrix using dispersion method and light irradiation. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed intercalation of Ag/AgCl nanoparticles into the clay layers. The as-prepared plasmonic photocatalyst exhibited an enhanced and stable photoactivity for the degradation of methylene blue (MB) under visible light. The high activity was attributed to the surface plasmon resonance (SPR) exhibited by Ag nanoparticles on the surface of AgCl. The detection of reactive species by radical scavengers displays that O2- and OH- are the main reactive species for the degradation of MB under visible light irradiation. The studies showed that 20 min illumination under visible light can complete degradation of methylene blue (MB), and indicate a high stability of photocatalytic degradation. The mechanism of separation of the photo-generated electrons and holes at the Ag/AgCl-MMT nanocomposite was discussed.

Facile and low temperature route to synthesis of CuS nanostructure in mesoporous material by solvothermal method.

The synthesis of CuS nanomaterial in MCM-41 matrix has been realized by chemical synthesis between MCM-41, copper sulfate pentahydrate and thiourea via a solvothermal method in ethylene glycol and water, separately. X-ray diffraction analysis (XRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fourier transform infrared (FT-IR) were used to characterize the products. At synthesized CuS/MCM-41 sample in ethylene glycol, X-ray diffraction and diffuse reflectance spectroscopy showed pure covellite phase of copper sulfide with high crystality. But prepared CuS/MCM-41 sample in water shows the covellite, chalcocite and the djurleite phase of copper sulfide nanostructures. The formation of CuS nanostructures was confirmed by FT-IR. Photocatalytic activity of CuS/MCM-41 nanocomposites was studied for degradation of Methylene Blue (MB) under visible light. The CuS/MCM-41 nanocomposite is more effective nanocatalyst than synthesized CuS/MCM-41 sample in water for degradation of methylene blue. Several parameters were examined, catalyst amount (0.1-1gL(-1)), pH (1-13) and initial concentration of MB (0.96-10ppm). The extent of degradation was estimated from the residual concentration by spectrophotometrically. The support size was obtained in the range 60-145nm by TEM. In the same way, the average size of copper sulfide in CuSMCM-41E and CuS/MCM-41W nanostructures were obtained about 10nm and 16nm, respectively.

Sulphonated cobalt phthalocyanine-MCM-41: an active photocatalyst for degradation of 2,4-dichlorophenol.

The photocatalytic activity of sulphonated cobalt phthalocyanine immobilized onto MCM-41 was investigated for decomposition of 2,4-dichlorophenol (2,4-DCP) in aqueous solutions. Immobilization of anion sulpho-cobalt phthalocyanine to the walls of MCM-41 was performed by pre-anchorage of 3-(aminopropyl)-triethoxysilane (APTES) onto MCM-41 via post-synthesis method. X-ray diffraction, nitrogen physisorption, diffuse reflectance spectroscopy, energy-dispersive X-ray and FT-IR methods were used to characterize the product. Photocatalytic efficiency of the prepared catalyst for degradation of 2,4-DCP was tested under illumination of UV-A and visible light. The results obtained reveal that the photocatalyst is very active in degradation of 2,4-DCP. The photodegradation process is completed within 3h using a dose of 0.6g/L of the catalyst under UV irradiation. The reactions follow a pseudo-first-order kinetics and the observed rate constant values change with 2,4-DCP concentrations. The reproducibility of the catalyst was tested. The reaction intermediates were identified by gas chromatoghraphy-mass spectrometry (GC-MS) technique.

Enhanced adsorptive and photocatalytic achievements in removal of methylene blue by incorporating tungstophosphoric acid-TiO2 into MCM-41.

The use of titania-dispersed materials in photocatalytic processes has been proposed as an alternative to the conventional bare TiO(2), in order to modify the surface area and activity of the catalyst. A homogeneously dispersed Keggin unit into TiO(2) was synthesized using tungstophosphoric acid (TPA) and titanium tetraisopropoxide. This compound was then loaded into MCM-41 by dispersing it in a suspension containing the mesoporous phase. Two other titanium-containing MCM-41 catalysts, Ti-MCM-41 and TiO(2)/MCM-41 were also prepared using isomorphous substitution synthesis method and impregnation method, respectively, for the sake of comparison. The prepared photocatalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption (BET) and chemical analysis. The catalysts were used to study degradation of methylene blue (MB) in aqueous solution. XRD result shows a pure anatase crystalline phase for TPA-containing TiO(2) indicating that there is good molecular distribution of tungstophosphoric acid into TiO(2) structure. Supported TPA-TiO(2) into MCM-41 shows both TPA-TiO(2) and MCM-41 characteristic X-ray reflections in the high-angle and low-angle parts of the XRD patterns, respectively. The experimental results show that adsorption is a major constituent in the elimination of MB from the dye solutions by the TPA-containing materials. Exploitation of both adsorption and photocatalytic processes speeds up the removal of the dye using the TPA-TiO(2)-loaded MCM-41 photocatalyst. The elimination of MB is completed within 15 min for a 30 mg l(-1) MB solution containing a catalyst dose of 100mg/100ml. The efficiencies of the other photocatalysts such as commercial TiO(2), Ti-MCM-41, TiO(2)/MCM-41 and TPA-TiO(2) for adsorption and degradation of MB were also studied and compared with that of the prepared catalyst.

Novel potentiometric membrane sensor based on 6-(4-nitrophenyl)-2-phenyl-4,4-dipropyl-3,5-diaza-bicyclo[3,1,0] hex-2-ene for detection of strontium (II) ions at trace levels.

A new PVC membrane strontium ion-selective electrode has been constructed using 6-(4-nitrophenyl)-2-phenyl-4,4-dipropyl-3,5-diaza-bicyclo[3,1,0] hex-2-ene (NPDBH) as a neutral ionophore. The electrode was prepared with 7% NPDBH (as ionophore), 57% acetophenone (as plasticizer), 30% PVC and 6% oleic acid (as lipophilic additive). The electrode responds to Sr2+ ion with a sensitivity of 28.2+/-0.5 mV/decade over the range 1.0 x 10(-6)-1.0 x 10(-1) mol L(-1) and in a pH range of 3.0-10.0. The limit of detection was 2.4 x 10(-7) mol L(-1). It has a response time of <20s and can be used for at least three months without any divergence in potentials. The proposed electrode shows good discrimination of Sr2+ ion from several cations. The effect of organic solvents on electrode response was examined. The results show that this electrode can be used in ethanol media up to 15% (v/v) concentration without interference. The isothermal temperature coefficient of this electrode amounted to 0.00019 V/ degrees C. The electrode was found to work well under laboratory conditions. It was successfully applied to the determination of strontium ions in human urine and bone digests.

Rapid determination of aluminum by UV-vis diffuse reflectance spectroscopy with application of suitable adsorbents.

Diffuse reflectance spectroscopy (DRS) can be used as a rapid and sensitive method for the quantitative determination of low amounts of aluminum. In this analytical technique, the analyte in samples are extracted onto a solid sorbent matrix loaded with a colorimetric reagent and then quantified directly on the adsorbent surface. Alternatively, colored aluminum complexes formed in solution can also be immobilized onto adsorbent surface and be measured by DRS technique. Octadecyl silica disk, methyltrioctylammonium chloride-naphthalene and MCM-41 were examined as adsorbents. Eriochrome cyanine R and quinalizarin were used as coloring reagents. Optimal sorption conditions were found for each system of analyte-reagent-adsorbent. The concentration of analyte is determined using the appropriate form of the Kubelka-Munk function. We obtained for each of the aluminium-reagent-adsorbent system a calibration curve by plotting the absorbance versus the log10(2)[Al(3+)]mugml(-1). The linear dynamic range extends over two orders of magnitude within 0.01-15mugml(-1) with little differences in the range and in the correlation coefficients among the adsorbents. We consider that for a rapid determination of aluminum a spot-test-DRS combination with a detection limit of 1.0x10(-2)mugml(-1) is the more facile and preferred technique.

Direct determination of triamterene by potentiometry using a coated wire selective electrode.

A coated wire triamterene-selective electrode based on the incorporation of a triamterene-tetraphenylborate ion-pair in a poly(vinylchloride) coating membrane was constructed. The influence of membrane composition, temperature, pH of the test solution, and foreign ions on the electrode performance were investigated. The electrode showed a Nernstian response over a triamterene concentration range from 1.0 x 10(-6) to 3.5 x 10(-2) M, at 25 degrees C, and was found to be very selective, precise, and usable within the pH range 4.5-7.5. The standard electrode potentials, E degrees, were determined at 15, 20, 25, 30, 35, 40 and 45 degrees C and used to calculate the isothermal temperature coefficient (dE degrees /dt) of the electrode. Temperatures higher than 45 degrees C seriously affected the electrode performance. The electrode was successfully applied to the potentiometric determination of triamterene hydrochloride both in pure solutions and in pharmaceutical preparations.

Self-association of rhodamine dyes in different host materials.

The aggregation of rhodamine 6G in liquid crystalline solution (anisotropic host) was studied using polarised spectroscopy and in a guest-host system. The self-association of rhodamine B was investigated in molecular sieves of type AlPO(4)-5 (microporous host) using diffuse reflectance spectroscopy. Also, the molecular interaction of rhodamines in normal solvents (isotropic hosts) was studied using visible spectroscopy for comparison. Therefore, the role of the host nature in the different phases on the self-association of the guest molecules has been investigated and compared. The absorption spectrum of the rhodamine dye in liquid crystalline host is affected by a specific interaction related to the alignment by the liquid crystal property as well as solvent polarity. Due to the existence of a large amount of water molecules absorbed into channels and cavities of aluminophosphate molecular sieve, the maximum absorption wavelengths of the dye loaded AlPO(4)-5 is affected by aqueous environment of the aluminophosphate pores.

Identification and estimation of extra-framework aluminium in acidic mazzite by diffuse reflectance spectroscopy.

Diffuse reflectance spectroscopy has been used to investigate structural modification of mazzite zeolite subjected to calcination, acid leaching and acetylacetone treatments. Extra-framework aluminium species, formed upon expulsion of aluminium from the framework, are detected by DRS because they are involved in aluminium-oxygen charge transfer transitions. Impregnation of the calcined ammonium-exchanged and acid leached samples with ethanolic acetylacetone will convert the broadened 260-280 nm band of extra-framework aluminium with distorted symmetry to a distinct well-defined 285 nm band. The appearance of this band is due to the transformation of the aluminium atoms with a different coordination number to structures with highly ordered octahedral symmetry. Washing the acetylacetone treated samples with hot ethanol leads to extraction of some of the complexed aluminium. The presence of an extracted aluminium triacetylacetonate complex in the eluant is verified by the same spectrophotometer used in its conventional mode. This suggests that a dual DR and UV-VIS spectrophotometry is an appropriate approach to study such topics.