Elaboration d'une membrane polymérique incorporant la tridodecylamine pour la détection de l'acide orange 10

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Caractérisation d'un biocapteur enzymatique impédimétrique destiné à la détection d'un pesticide organochlore.

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Electrochemical Characterization of Enzymatic Impedimetric Biosensor Destined to Detect Organochlorine Pesticide: the Diclofop-methyl

Preservation of aquatic ecosystems requires early warning tools such as biosensors for in situ monitoring and continuously. Such tools can provide information about the nature of pollutants condition be designed to meet specific manner. This work proposes an impedimetric biosensor, using a bacterial enzyme (Condida Rugosa lipase) immobilized in an organic matrix composed of BSA (bovine serum albumin) and glutaraldehyde, capable of detecting organochlorine pesticides (Diclofop-methyl) state trace in aqueous media. Moreover, these measurements were carried out by varying a number of parameters characteristic of the system being studied in order to better define the role of the different elements involved in the development of the receiving part of the sensor as follows: Composition of the membrane, effect of temperature and the effect of the pH of the medium. The results show that the developed biosensor provides answers in an area of very low concentrations of the order of 5.99x10-14 - 5.88x10-3 g/L and a detection limit of 5.99x10-14 g/L for Diclofop-methyl. This biosensor detects the pollutant in a temperature range between 20 °C and 40 °C. We also studied the selectivity of the detection of the target substance in the presence of interfering with some heavy metals (cadmium, cobalt, zinc and lead) and other organophosphorus and organochlorines pesticide

Development of a hexavalent chromium ISFET sensor with a polymeric membrane including tributylphosphate

International audienceThis paper presents a first report on chromium ISFET (ion-sensitive field effect transistor) based on a polymeric membrane (siloprene) including an ionophore (tributylphosphate) sensitive for hexavalent chromium. The sensor sensitivity as a function of the pH was studied; its value is minimum in a pH interval from 5.5 to 7.5. The sensitivity for hexavalent chromium was found to be 15 mV/Ioga(Cr6+) in the range of 10(-4) to 10(-2) M. The detection limit was found to be 10(-5) M. The studied interfering ions are Pb(II) and Cd(II) that do not represent a great perturbation upon the response for hexavalent chromium. (c) 2005 Elsevier B.V. All rights reserved

Microstructure and optical dispersion characterization of nanocomposite sol-gel TiO2-SiO2 thin films with different compositions

International audienceNanocomposite TiO2-SiO2 thin films with different compositions (from 0 to 100 mol% TiO2) were deposited by sal-gel dip-coating method on silicon substrate. Crystal structure, chemical bonding configuration, composition and morphology evolutions with composition were followed by Raman scattering, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy respectively. The refractive index and the extinction coefficient were derived in a broad band wavelength (250-900 nm) from spectroscopic ellipsometry data with high accuracy and correlated with composition and microstructure. Results showed an anatase structure for 100% TiO2 with a grain size in 6-10 nm range. Whereas, the inclusion of SiO2 enlarges the optical band gap and suppresses the grain growth up to 4 nm in size. High TiO2 dispersion in SiO2 matrix was observed for all mixed materials. The refractive index (at lambda = 600 nm) increases linearly with composition from 1.48 (in 100% SiO2) to 2.22 (in 100% TiO2) leading to lower dense material, its dispersion being discussed in terms of the Wemple-DiDomenico single oscillator model. Hence, the optical parameters, such optical dispersion energies E-D and E-d, the average oscillators, strength S-0 and wavelength lambda(0) and the ratio of the carrier concentration to the effective mass N/m* have been derived. The analysis revealed a strong dependence on composition and structure. The optical response was also investigated in term of complex optical conductivity (sigma) and both volume and surface energy loss functions (VELF and SELF)

Comparative Study of Responses of Two Enzymatic Biosensors Based on Lipase from Candida rugosa and Porcine Pancreas for Detection of Diclofop-Methyl

International audienceThe objective of this study was to evaluate the immobilization of lipase on an organic matrix by reticulation method, aiming at its application in the detection of organochlorine pesticide. The biologically inactive protein of bovine serum albumin (BSA) and glutaraldehyde were used for immobilizing lipase from a microbial source ( Candida rugosa CRL ) and animal cells (porcine pancreatic lipase, PPL). Use of this immobilized preparation was extended to the realization of two different origins of a miniaturized enzymatic biosensors is presented for the electrochemical detection of a large range of organochlorine pesticide (diclofop-methyl) in phosphate buffer saline (PBS) were observed experimentally. The best responses of biosensor were obtained for PPL with a high sensitivity to organochlorine pesticide in the concentration range of 5.99*10-12 to 5.89*10-2g*L-1, whereas a linear response of CRL for diclofop-methyl was obtained. The lipase biosensors exhibits the advantage of a simple fabrication procedure, wide dynamic range and a lower detection limit (5.99*10-12 g*L-1 for diclofop-methyl). The impact of heavy metals as well as organophosphorous and other organochlorine pesticides was also studied

Effect of copper content and sulfurization process on optical, structural and electrical properties of ultrasonic spray pyrolysed Cu2ZnSnS4 thin films

This paper reports the effect of copper content and of the sulfurization process (using elemental sulfur vapor) on the growth, structure, elemental composition, and on the optical and electrical properties of Cu2ZnSnS4 (CZTS) thin films deposited on glass substrates using ultrasonic Spray Pyrolysis. For this purpose, a series of aqueous solutions consisting of copper (II) and tin (IV) chlorides, zinc (II) acetate and thiourea with different copper concentrations (x = Cu/(Zn + Sn) = 0.8, 1, 1.2 and 1.4 while Zn/Sn = 1) were prepared. X-ray diffraction, Raman spectroscopy, scanning electronic microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, ultraviolet–visible–near infrared absorbance spectroscopy and sheet resistance analyses were used to follow the evolution of the investigated properties. The results outlined a Kesterite type CZTS phase and a secondary copper sulfide (Cu2-xS) phase, and their ratio strongly depends on the copper salt concentration and heat-treatment atmosphere. No traces of secondary phases of zinc or tin sulfides are found while high purity CZTS was obtained with the post-sulfurized film at x = 1.2. It was found that the application of additional sulfurization enhances the grain growth to reach 300 nm in size and induces significant improvement of both CZTS crystallinity and electrical conductivity. The optical band gap ranges between 1.44 and 1.57 eV depending on the composition and the sulfur deficiency is strongly reduced leading to Cu-poorer and Zn-richer compounds, as compared to those annealed in nitrogen atmosphere