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In this study, a sensor based on tetrabutylammonium octamolybdate (Bu4N)4 (Mo8O26) (POM) has been immobilized on the indium tin oxide (ITO) coated glass substrates using the poly(allylamine hydrochloride) (PAH) for a selective determination of cloxacillin. The morphology and the hydrophobicity of the modified electrodes were examined using the scanning electron microscopy (SEM) and contact angle measurements (CAM), respectively. The electrochemical impedance spectroscopy (EIS) is used to follow the detection progress of cloxacillin in the darkness and under illumination with the lowest limits of detection (10–11.5 M) and a wide linear range of 10−11 to 10−7 M. The evolution of the equivalent electrical circuit’s parameters was studied to establish the ability of the light excitation to improve the cloxacillin detection.

A new fluoroborophosphate glass doped with different amount of CrF3 were prepared via the melt-quenching method. These glasses were characterized by several techniques. The amorphous nature of the glass was evidenced by X-ray diffraction. Raman and FTIR were used to determine the functional groups composing the glass network. It was demonstrated the formation of B-O-P bond which replace some of the P-O-P bond and ensure the bonding of phosphorus and boron groups. Electron paramagnetic resonance (EPR), optical absorption and photoluminescence (PL) investigation have shown that Cr3+ ions have a preference to be located at weak field with distorted octahedral sites and they are mainly dispersed in phosphorus rich environment with fluorine or mixed fluorine/oxygen surrounding anions. Cr3+ sites dispersion was also evidenced by analyzing the temperature dependence of the PL spectra and the PL decay.

In this work, we present a safe and relatively simple procedure to eliminate hydroxyl groups from Er3+ and Yb3+ codoped new flurotellurite glasses. It was shown that adding a convenient amount of BaF2 as drying agent reduced the absorption coefficient and the concentration of hydroxyl groups inside the glass samples. However, to remove efficiently water from the glasses, it was necessary to subject the samples to supplementary heat treatment in two steps. A drastic decrease of the density of hydroxyl groups accompanied with a significant enhancement of the erbium emission was observed after the heat-treatment procedure. The obtained results showed that this method might be a veritable alternative to obtain nearly water free tellurite glasses suitable for many optical devices with small sizes or thickness. However, for a good use of this procedure, we tried to elucidate what has happened at the microscopic scale for the glass taking as a guide the available explanations dealing with the removal of water from silica-based glasses.

International audience; Silicophosphate glasses (SiO2-P2O5) doped with Eu3+ ions were synthesized by the sol-gel process. Optical properties of these glasses were investigated by means of emission spectra and lifetime measurements. The Fluorescence Line Narrowing (FLN) technique was also used to explore the local structure around the Eu3+ ions in this host and to understand the role of phosphate as a codopant. As it is the case for aluminum, the ability of phosphate to avoid the rare earth clustering was investigated, and the role of this codopant in modifying the local order around the rare earth ion was evidenced. The analysis of the FLN spectra and lifetime measurements is consistent with this interpretation. Molecular Dynamics simulations were performed to evaluate and confirm these structural features. Two classes of europium sites were distinguished in agreement with the experimental characterization.

International audience; In this work, we investigate the effect of co-doping with CdS nanoparticles on the photoluminescence properties of Eu3+ doped silicophosphate glass prepared via the sol gel method. Infrared spectroscopy (FTIR) revealed the insertion of phosphorus within the silicate network. XRD and TEM analyses revealed the presence of CdS nanoparticles dispersed in the glass matrix. Based on the optical study and the effective mass theory for spherical quantum dots, it was found that CdS nanocrystals have a gap of nearly 3.53 eV and a size of 2.42 nm. The enhancement of Eu3+ emission induced by CdS nanocrystals and thermal annealing was assigned to either an energy transfer via defect states or structural alteration of the glass network around the rare earth ions.

In this study, we first describe the synthesis of the triflato(5,10,15,20-tetrakis(4-metoxyphenyl) porphyrinato) iron(III) complex with the formula [FeIII(TMPP)(SO3CF3)] (P1). This species were characterized by proton NMR and IR. Then optical and electrical properties of P1 thin films have been investigated. The triflato iron porphyrin film exhibit an absorption spectrum with a resolved electronic structure in the UV–vis range and the energy gap was determined by the Tauc method. Electrical properties of the ITO/P1/Al structure have been investigated by I–V characteristics and impedance spectroscopy measurements. The conduction is governed by space-charge-limited current (SCLC) mechanism. The impedance spectroscopy study showed a hopping transport process. Its interaction with Bisphenol A (BPA) was then investigated by UV–vis spectroscopy in a sensing window of 10−9–10−4 M. The iron-porphyrin species shows a sensitive response to BPA, which induces an absorbance change to the Soret band. The interaction mechanism of P1 with BPA involved a coordination interaction.

International audience; The effects of Na2SO4 substitution to Na2O on the structural and electrical properties of a sodium borophosphateglass system prepared by the melt/quenching method were investigated by means ofdifferent techniques. The amorphous nature of the glass was evidenced by X-ray diffraction (XRD).Differential scanning calorimetry (DSC) has showed a decrease of glass transition temperature (Tg) whiledensity measurements showed an increase of the molar volume Vm of the glass with the addition ofNa2SO4. Raman and infrared (FTIR) spectroscopies have revealed a significant structural change whichconfirms the behavior of Tg and Vm of the glass. Impedance measurements showed that the overallelectrical behavior originates from bulk contribution, whereas the frequency dependence of ac conductivitydoes not seem to follow the simple Jonscher's power law due to the electrode polarizationeffects. Moreover, the dc conductivity exhibits an Arrhenius-type behavior with temperature. Thedecrease of the activation energy and the increase of the electrical conductivity with the additionNa2SO4was discussed based on the results of the structural investigation of the glass.

A series of Er 3+ /Yb 3+ co-doped novel fluoro-tellurite glasses was prepared following the melt quenching technique. Raman spectroscopy was used to analyze the functional groups present in the glass network and to determine the phonon energy of this glassy system. The optical properties of the glasses were characterized by different techniques such as optical absorption, photoluminescence (visible and near infrared) and time-resolved spectroscopy. Using optical absorption data and Judd-Ofelt theory, several spectroscopic parameters such as transition probabilities, radiative lifetimes and branching ratios were estimated for different Yb 2 O 3 contents. The up-conversion process, after excitation with an infrared radiation at 980 nm, was examined and the different mechanisms involved in these emissions such as excited state absorption, energy transfer processes and cross-relaxation are discussed. The emission cross-section corresponding to the 4 I 13/2 level was calculated using McCumber theory. The experimental lifetime and the quantum efficiency corresponding to the 4 I 13/2 level were also determined to evaluate the appropriateness of the host matrix for the fabrication of laser materials and broadband amplifiers. It was found that the effective bandwidth is larger and quantum efficiency and the emission cross-section are higher than those obtained for others vitreous systems, which suggests that the proposed glasses can be nominated as suitable host material for new Er 3+ /Yb 3+ codoped broadband optical amplifiers and for the development of optical devices.

This study describes an investigation of the sensitivity of the azo-calix[4]arene/poly(3,4-ethylenedioxythiophene)/poly-(styrenesulfonate) (PEDOT:PSS) thin film deposited on the indium tin oxide (ITO) electrode surface toward aluminum ions (Al3+) under light excitation. Thin films were deposited by the spin-coating technique. Adhesion of these films to the ITO surface was highlighted by performing contact angle measurements. Then, interfaces of the azo-calix[4]arene/PEDOT:PSS thin film were characterized by impedance measurements using electrochemical impedance spectroscopy. Obtained impedance spectra were fitted using an equivalent circuit. Finally, evolutions of the different components of this circuit were studied. These evolutions show that the sensitivity of the azo-calix[4]arene/PEDOT:PSS/ITO electrode is remarkably improved under illumination.

A new hybrid monolithic silica xerogel containing sucrose has been synthesized via the sol–gel method. The resulting sucrose silica xerogels were exposed to gamma radiation with a dose in the range of 10–100 kGy. The effect of gamma rays on the physical and structural properties of sucrose silica xerogels was investigated by Fourier transform infrared spectroscopy (FTIR) and UV visible spectroscopy. The results of FTIR spectroscopy show that the irradiation process causes changes in the network's structure by inducing defects. The UV visible spectra present three main band defects; E′ center, Non-Bridging Oxygen Hole center (NBOHC) and carbonyl radicals in irradiated sucrose silica xerogel samples. Additionally, the results show that the values of optical band gap energy depend on irradiation. Therefore, generated defects suggest that the behavior of sucrose silica xerogels was modified from an insulator (Eg=5.82 eV) to a semiconductor (Eg=3.16 eV) under gamma irradiation.

In this work, we investigate the effect of BaF2 on the structural and optical properties of Er3+/Yb3+ co-doped fluoro-tellurite glasses prepared by the melt quenching technique. Good thermal stability and low phonon energy of this glassy system were found using differential scanning calorimetry and Raman spectroscopy, respectively. Infrared measurements showed a significant shift of infrared longwave transmission limit by increasing fluoride content. By Judd-Ofelt theory, the local environment surrounding the Er3+ ions was analyzed and several spectroscopic parameters such as radiative lifetimes, quantum efficiency, optical bandgap, effective bandwidth, emission cross-section and figure of merit of 4I13/2→4I15/2 transition were estimated and optimized with respect to the BaF2 content. Due to the strong absorption of Yb3+ at nearly 1000 nm, a high quantum efficiency of Er3+ emission at 1530 nm (>100%) was detected and an upconversion mechanism was suggested to explain this significant enhancement. The results show some remarkable spectroscopic parameters attributed to the 4I13/2→4I15/2 transition, which have a major importance in many optical devices, and the investigated glass may be proposed in particular for conception of luminescent concentrators for germanium-based solar cells.

Cadmium sulfide (CdS) nanoparticles were synthesized by a novel wet chemical route with various organic thiol stabilizers. Systematic experimental studies, including X-ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), photoluminescence (PL) spectroscopy, and time-resolved photoluminescence (TRPL), have evidenced that the stability, crystallinity, and optical properties of the CdS nanoparticles are affected by the organic groups which generate significant effects in surface reconstruction. Particle size was evaluated from UV–vis spectroscopy using the effective mass approximation (EMA) method and from XRD patterns based on Scherrer׳s formula. The S–H vibrations are not detectable in the infrared (IR) spectra of any of the bound ligands, which are expected for thiols covalently bound to the surface of nanoparticles. PL studies reveal that the emission from the nanostructures is not much influenced by the surface states, indicating a good passivation of the particle׳s surface. The time-resolved measurements reveal a biexponential decay behavior. The fast decay component is attributed to the recombination of core states, while the slow decay component of PL is associated with the charge-carrier recombination process with the involvement of surface states.

Two new Zinc phtalocyanine, ZnPcR1 and ZnPcR4, with peripheral mono and tetra quinoleinoxy substituents of the phtalocyanine ring, were characterized to investigate their optical and electrical properties. The modification of the chemical structure allows the elongation of the π-conjugation, leading to an enhanced solubility as well as a broadening of the ZnPcR1 and ZnPcR4 absorption spectra. The UV–Visible absorption spectra show a typical behavior of phtalocyanine for the two π-conjugated systems with an optical band gap of 1.70 and 1.74 eV for ZnPcR1 and ZnPcR4 respectively and the Photoluminescence study exhibits a green emission for both compounds. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels were estimated using cyclic voltammetry analysis and the calculated electrochemical gap was found to be equal to the optical one. Current–voltage characteristics and impedance spectroscopy measurements performed on sandwich structures ITO/phtalocyanine derivatives/Al are used to elucidate the conduction mechanisms. The static electrical characterizations showed a space charge limited conduction with exponential trap distribution at high applied bias voltage. The impedance spectra were discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with a resistor Rs. The evolution of the electrical parameters deduced from fitting of the experimental data is discussed. The conduction mechanism revealed by I–V characteristics is in agreement with the impedance spectroscopy results.

The aim of this work was to study the electrochemical behavior of gold electrode which was modified with p-tert-butylcalix[6]arene membrane and this in the presence of different nickel ions based concentrations in order to form a nickel electrochemical sensor. For that, impedance-spec- troscopy characteristics have been investigated. The obtained results were then modeled by appropriate equivalent circuit aiming at elucidating the electrical properties of the modified gold transducer. A correlation between the present impedimetric results and previous potentiometric ones was achieved traducing then a fast ionic transfer.

A modified ITO electrode based on conducting polymer (MEH–PPV) matrix doped with the calix[4]arene molecules (β-ketoimine calix[4]arene) is deposited by spin coating. The carrier transport mechanism of the MEH–PPV and MEH–PPV:β-ketoiminecalix[4]arene films is investigated by using I – V characteristics measurements. The conduction mechanisms in these thin films are identified to be a space-charge-limited current (SCLC). The dielectric behavior of the MEH–PPV and the composite β-ketoimine calix[4]arene/MEH–PPV thin films are investigated by impedance spectroscopy (IS). The Cole–Cole plots are studied showing single semicircles and the solid interfaces are modeled by an equivalent circuit. The characteristics of chemical sensors based on MEH–PPV and MEH–PPV doped β-ketoimine calix[4]arene thin films for the detection of Cu 2+ and Na + ions are investigated by electrochemical impedance spectroscopy (EIS). The experimental impedance data of the modified electrodes are modeled by an equivalent circuit using the Z-View software. The inclusion of calixarene molecules into conducting polymer (MEH–PPV) exhibited considerable rise charge transfer resistance and improves sensing properties.

Optical, electrical and ion sensing properties of β-ketoimine calix[4]arene thin films have been investigated. These calix[4]arene derivative films exhibit absorption spectra with a resolved electronic structure in the UV–vis and the energy gap was found to be 3.65 eV. Electrical properties of ITO/β-ketoimine calix[4]arene/Al devices have been investigated by I – V characteristics and impedance spectroscopy measurements. The conduction is governed by space-charge-limited current (SCLC) mechanism. The impedance spectroscopy study showed a hopping transport process, a typical behavior of disordered materials. The device was modeled by a single parallel resistor and capacitor network in series with a resistance. The β-ketoimine calix[4]arene was used for the conception of the novel optical chemical sensor and the detection of Cu 2+ ions was monitored by UV–visible spectroscopy. The linear dynamic range for the determination of Cu 2+ has been 10 −5 –10 −3.7 M with a detection limit of 10 −5 M. The characteristics of this optode such as regeneration, repeatability, reproducibility, short-term stability, life time and ion selectivity have been discussed.

Conducting polymer can be used as the polymer matrix of the ion sensitive membrane (containing electroactive sites), which would exhibit intrinsic mixed ionic and electronic conductivity. In this work, a soluble poly( p -phenylene vinylene) derivative (MEH-PPV) has been used as the electroconducting polymer to immobilize the s-ketoimine calix[4]arene derivative. Indium-thin oxide (ITO) electrode coated with the thin films of MEH-PPV and composite MEH-PPV/s-ketoimine Cal[4] are designed for the determination of trace amounts of Hg 2+ ions. Surface morphology properties were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The presented results show that the incorporation of calixarene derivative into MEH-PPV polymer improved the surface smoothness. Contact angle measurements were used to study hydrophobicity and surface energy properties of thin films. We observed that the best adhesion on the ITO surface is for the MEH-PPV/s-ketoimine Cal[4] surface due to the presence of (OH) groups coming from the molecules of derivative calix[4]arene. Thin films were characterized by electrochemical impedance spectroscopy (EIS) in the dark and under illumination. The impedance behavior of the modified electrodes is modeled by an equivalent electrical circuit using the Z-View software. From the impedance plots, the bulk resistance and ionic conductivity of the membranes is an important factor determining the ability of ions to pass across the membrane. Marked differences in the ionic conductivity are observed as a function of the light excitation. The charge transfer processes at the electrode/electrolyte interface was carefully examined in the dark and under illumination. Optical excitation of both membranes revealed that the sensing activity of the MEH-PPV/s-ketoimine Cal[4] modified electrode can improve the measuring sensitivity of Hg 2+ ions compared to the MEH-PPV modified electrode.

In the present study we have synthesized CdS semiconducting quantum dots by reverse micelle method using dodecanthiol (C 12 H 26 S) as the capping agent. The synthetic medium consists of a quaternary water/Sodium dodecyl sulfate (SDS)/buta-1-ol/hexane microemulsion. The size of the particles was controlled by changing the molar ratio W =[H 2 O]/[SdS], where [H 2 O] and [SdS] are the molar concentrations in hexane of water and SdS respectively. The CdS nanoparticles were embedded in a new PPV derivate named Fluorinated Bisphenol A P-phenylenevinylene (BPAF-PPV). Fourier transform infrared spectroscopy (FT-IR) showed a strong interaction of thiol groups with CdS nanoparticles. Blue shift of the optical absorption onset is observed due to quantum size effect. The band gap and particle sizes of the nanoparticles were deduced from optical absorption spectra and the use of an effective mass approximation (EMA) model. Photoluminescence spectroscopy evidenced a charge transfer process via the interface between BPAF-PPV/CdS nanoparticles.

Selective and sensitive optical sensor membranes (optodes) were elaborated to detect cations in aqueous solutions. The sensing films are based on chromogenic calix[4]arene derivatives. The optode membranes were studied using UV/Vis absorption spectroscopy measurements. The sensitivity of the optode has been tested for Pb 2 + , Cd 2 + , Mg 2 + and Eu 3 + ions at pH 6.8. The results showed a good selectivity response towards Eu 3 + . Low selectivity coefficients were observed for Cd 2 + and Mg 2 + where Pb 2 + can be considered as interfering ions. The characteristics of this optode such as response time, regeneration, reproducibility and lifetime are discussed.

This work explored the development of impedimetric sensors based on conducting polyaniline (PANI) and PANI- β -CDpNH 2 thin films, formed by the complex inclusion of polyaniline with the modified β -cyclodextrin with amino groups. Thin films about 100 nm were deposited by thermal evaporation on gold electrodes. These thin films were characterized by the wettability technique for hydrophobicity analysis. The electrical properties of these polymer films have been studied by electrochemical impedance spectroscopy (EIS) technique. This study has revealed, according to an equivalent circuit fitting the experimental parameters, that PANI- β -CDpNH 2 film is more conductive than PANI one. This result was explained by the PANI conformation changes from coiled and disorderly chain to rodlike one coated in the cavities of β -CD. Finally we have studied the electrochemical response of these electrodes towards Pb 2+ cations in the aim to probe the contribution of PANI inclusion with β -CDpNH 2 molecules to the enhancement of the sensitivity and recognition properties of these later. We have found that PANI- β -CDpNH 2 film exhibits a good sensitivity towards the Pb 2+ cations.

In this work, we report the impedance spectroscopic investigation of the effect of the thin film type on the selectivity of gold/azo-calix[4]arene electrodes. For this purpose, two C1 and C3 azo-calix[4]arene derivative molecules, used as thin films, are deposited by spin-coating process on the gold surface. These thin films were first studied using contact angle measurements. This revealed a less hydrophobic character for C3 thin film, which has been attributed to the presence of hydroxyl groups at the lower rim. The sensitivity study, by Electrochemical Impedance Spectroscopy (EIS), towards Cu 2+ and Eu 3+ cations, has showed that the C3 thin film is more sensitive and selective towards Eu 3+ than C1. This best performance is due to the presence of two ester groups acting as clips and leading to more complexation stability. The EIS results were modeled by an appropriate equivalent circuit for the aim of elucidating electrical properties of thin films. This modeling has exposed that C3 thin film presents lower ionic conductivity and limited diffusion phenomenon at the interface.

Les cyanobacteries en general, synthetisent et secretent dans leur milieu de culture des substances diverses a activite algicide, antibiotique, cytotoxique et immunosuppressive afin de predominer dans leurs ecosystemes. Chez l’espece Arthrospira platensis, ces substances et surtout leurs effets sont tres peu etudies. Notre travail vise la mise en evidence et la quantification de trois activites biologiques de metabolites extracellulaires de la cyanobacterie Arthrospira platensis, originaire du lac Tchad, a savoir l’activite cytotoxique sur les cellules Caco et Vero, l’activite antibacterienne sur les bacteries Gram positives Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus et sur les bacteries Gram negatives Pseudomonas aeruginosa, Escherichia coli et Salmonella paratyphi et l’activite stimulatrice de la division cellulaire sur la microalgue Cosmarium lundellii.

Commercial silicate glass has been investigated as a possible high dose dosimeter using an UV–vis spectrophotometer. Glass samples were irradiated by 60Co γ rays and the results compared with those obtained with 3.4 and 8.4 MeV electron beams. The irradiated samples showed rapid fading at room temperature immediately after irradiation. In order to improve the stability of absorbance, glass samples were submitted to post-irradiation thermal treatments (150 °C for 20 min). The influences of the dose, type and energy of the ionizing radiation on the fading characteristics and on the response of the irradiated and thermally treated glasses were studied. Dependence of the glass response on the temperature during gamma irradiation in the range −3 to 80 °C is reported. The reproducibility to reuse glass dosimeter by thermal bleaching the radiation induced colour centres at 300 °C for 30 min was also investigated. Calibration curves in the range 0.1–17 kGy were obtained by using in-plant calibration techniques against transfer standard alanine dosimeters in the Tunisian semi-industrial gamma irradiation facility.

International audience; The nanomorphology, optical and electrical properties of vacuum-deposited azo-calix[4]arene thin films have been investigated. The nanostructured films exhibit absorption spectra with a resolved electronic structure in the UV-vis and a blue photoluminescence emission at about 430 nm independent of the excitation wavelength. The current-voltage (I-V) characteristics of ITO/azo-calix[4]arene/Au devices have been studied. The I-V dependence follows a power law, I ∝ Vm, which is typical of a space-charge-limited current. Moreover, from the I-V measurements, we have estimated the effective hole mobility of not, vert, similar7.5 × 10−6 cm2/V s in the vacuum-deposited azo-calix[4]arene thin films. Using impedance spectroscopy over a broad frequency range, i.e. 100 Hz to 10 MHz, it is found that the ac behavior of an ITO/azo-calix[4]arene/Au device shows several features, described by the simple RC circuit representing an undepleted bulk region. Values of the electrical circuit parameters deduced from fitting experimental data to the model have given a dielectric relaxation time in the millisecond range.

A commercial glass has been investigated using UV–Vis spectrophotometry to study the gamma radiation response of this material andto evaluate its dosimetric characteristics: dose response, room temperature fading, effect of relative humidity during post-irradiation storage,temperature during irradiation and the dose rate effect. The overall uncertainty was also estimated.The obtained results demonstrate that the influence quantities on the glass response might be very significant and suitable corrections areindispensable.© 2008 Elsevier Ltd. All rights reserved. Keywords: Commercial glass; Gamma rays; Dosimetry; Environment effects 1. Introduction Several kinds of dosimeters are widely used for the processcontrol of the radiation processing applications such as steril-ization of medical devices, food preservation and other appli-cations. Especially dosimeters based on the radiation-inducedcolouration properties are also extensively used for the routinemeasurements of the absorbed dose. Most radiation processesare conducted under a wide variety of surrounding atmosphericconditions and, in fact, the response of dosimeters is signifi-cantly influenced by temperature during irradiation and doserate (McLaughlin et al., 1989). Since environmental conditionsmaydifferbetweencalibrationandpracticaluses,responsevari-ations of routine dosimeters with the surrounding conditionsmust be determined in order to correct such systematic errors.Some investigators have done researches on an availablewindow glass as a high dose dosimeter (Caldas and Teixeira,2002; Rodrigues, 2002). A suitable response has been shownwhen evaluated by spectrophotometer at specified wavelengthsin visible spectrum. The radiation induced colouration inglass can be affected by many environmental factors including

Wettability studies have been performed to probe the surface properties of ITO substrates, aimed to be used as hole injecting electrode in OLEDs. The elimination of organic contaminants upon the cleaning treatment (ultrasonic bath in organic solvents) leads to an increase of the free energy of the ITO surface becoming hydrophilic. The surface energy components calculated from the Van Oss model show the appearance of a basic component upon the cleaning treatment. A thermal treatment at 100 °C for 3 h leads to a decrease of the surface free energy due to surface dehydration. These properties are attributed to the hydroxides formed at the ITO surface inducing improved adhesion at the ITO/polymer interface. The ITO surfaces have been functionalised with a chloroethylphosphonic acid mono-layer to increase their stability. The appearance of an acid–base component leads to a dipolar character of the ITO surface. The formation of a compact layer of a spin coated poly(phenylenevinylene) derivative induces the shielding of the ITO basic character. The weakening of the near infrared absorption associated to ITO free carriers confirms the formation of a dipole layer at the interface with the molecular layer in contact with ITO. Improved injection properties, shown by the current/voltage characteristics, result from the interface modifications.

International audience; Electrical measurements have been performed on spin-coated azo-calix[4]arene derivative on pre-cleaned indium thin oxide (ITO) substrates using current versus voltage, capacitance versus voltage and impedance spectroscopy measurements. The nature of trap states in single layer ITO/azo-calix[4]arene derivative/Al organic diodes has also been investigated. The energy band gap of the thin film containing calixarene derivative has been measured by UV-Vis absorption spectroscopy and is about 2.77 eV. The current-voltage characteristics have shown ohmic behavior at low voltages. At high applied bias the I-V characteristics can be successfully modeled by space-charge limited current (SCLC) theory. The impedance dependence of bias and frequency is discussed in terms of the presence of a depletion layer in the bulk. The device is accurately modeled, in a range of frequency between 100 Hz and 1 MHz, as a single parallel resistor and capacitor network placed in series with a resistance. Their values deduced from fitting experimental data to the model have given a dielectric relaxation time in the ms range and an exponential trap distribution.

Thin films of two partially benzylated β-CDs (β-cyclodextrins) were used to functionalize ITO (indium tin oxide) and Si/SiO 2 substrates which were deposited by spin coating technique, to fabricate respectively a diode device and an EIS (electrolyte–insulator–semiconductor) sensor. We have studied electrical properties of ITO/β-CDs (Bz) n =5,10 /Al diodes by means of current–voltage measurement and impedance spectroscopy. The application of these new modified β-CD (Bz) n =5,10 in the field of chemical sensors has been studied. Electrochemical capacitance measurements with EIS structures were made to test and calibrate physico-chemical sensors with regards to their sensitivity and selectivity. The sensing properties of these partial benzylated β-CD films towards Pb 2+ in aqueous solution for sensor application were tested. A significant effect of the average of benzylation degree on both electrical and sensing properties has been investigated.

A commercial window glass has been investigated as a routine high dose dosimeter for gamma irradiation. The irradiated samples showed rapid fading at room temperature immediately after irradiation. This short-term rapid fading was followed by a slow fading at long-term. This strong initial fading is a problem for dosimetry purposes. However, when the dosimeter is measured at the same time interval after irradiation, it maintains proportionality to dose. Calibration curves have to be used for different time intervals after irradiation. In order to improve post-irradiation stability dosimeters were submitted to different post-irradiation thermal treatments from (−20) up to 150 °C. After that, optical absorbance measurements were carried out up to 2 months at room temperature. The heating at 150 °C for 20 min was found to be the most suitable procedure for the removal of unstable entities responsible for the initial rapid fading. Due to these heat treatments, variation of response was found almost negligible 24 h after irradiation for several months. Calibration curves demonstrated the applicability of this glass as routine dosimeter in the dose range of 0.5–90 kGy.

Kinetic characterizations of impedimetric sensors having as transducers gold electrodes and as recognizing elements p - tert -butylcalix[4,8,12]arene were accomplished. Calixarene membranes were first studied using contact angle measurements. These revealed that all membranes exhibited hydrophobic and rough behaviours. Besides, based on the Van Oss model, surface energy components were determined and the main difference for the basic energy component was related to the calixarene conformation where hydroxyl groups were pointing towards gold surface. Electrochemical impedance spectroscopy results were modeled by appropriate equivalent circuits for the aim of elucidating electrical properties of calixarene functionalized gold electrodes. As results, a fast ionic transfer took place for p - tert -butylcalix[4] based impedimetric sensor, and a slow ionic transfer occurred for both p - tert -butylcalix[8,12] based impedimetric sensors. These behaviours were well accommodated with potentiometric outcomes that were previously encountered.

A sensing material based on calix[4]arene molecules (Azo-C[4]) dispersed in a conjugated polymer (MEHPPV) is deposited by spin coating onto a transparent conducting substrate (ITO) to fabricate new chemical sensors. The electrochemical properties of the sensor are investigated by impedance spectroscopy. Transfer and ion diffusion processes of metal cations (Cu2+, Eu3+) in the Azo-C[4]-MEHPPV membranes are studied. The calixarene molecule behaviour into the polymer membranes is characterised by impedance spectroscopy showing the cation complexation by both, Azo-calix[4]arene and MEHPPV, components of the membrane. The differences in selectivity are found to be represented by variations in the bulk resistance of the membrane (Rm) and in the charge transfer resistance (Rtc) of the interface. The impedance behaviour of the Azo-C[4]-MEHPPV electrodes is modelled by an equivalent electrical circuit. Optical excitation tests of these membranes show that the sensing activity of the calixarene molecules entrapped in the polymer matrix is preserved.

In-situ characterisation of the n + -GaAs/HF:Et-OH interface is studied by current–voltage, J ( V ). The experimental current-potential exhibits the presence of three potential regions, which are attributed to different reaction mechanisms between HF and n + -type GaAs surface. Depending on HF concentration a current peak appears in the J ( V ) characteristics. Scanning electron microscopy (SEM) images of samples at different point of the J ( V ) characteristic exhibits different surface morphologies which depend strongly on the electrochemical anodization conditions.

International audience; Thin films of poly[2-methoxy-5-(20-ethylhexyloxy)-1,4 phenylenevinylene] (MEH-PPV), 5,17-bis(4-nitrophenylazo)-26,28-dihydroxy-25,27-di(ethoxycarbonylmethoxy)-calix[4]arene (azo-calix[4]arene) and MEH-PPV doped azo-calix[4]arene, with 30 wt% and 70 wt% doping ratios, were prepared from chloroform solution by spin coating technique on quartz and ITO substrates. Morphological and optical properties of the samples were investigated by scanning electron microscopy (SEM) and UV-visible spectrophotometry techniques, respectively. Further, the charge carrier transport properties and conduction mechanism of the composite MEH-PPV:azo-calix[4larene thin films based junction were studied by using current-voltage (1-V) characteristics and dielectric spectroscopy technique. I-V characteristic of ITO/MEH-PPV:azo-calix[4]arene/Al devices showed that the space charge limited conduction (SCLC) dominates in the high voltage region. Moreover, frequency dependence of ac conductivity obeys Jonscher's universal power law. Finally, dielectric constant (epsilon'), dielectric loss (epsilon '') and loss tangent (tan delta) were investigated as function of amount of azo-calix[4]arene in the MEH-PPV polymer matrix.

A novel optical sensor for sensitive and selective determination of copper ions in aqueous solution based on a novel calix[4]dicyano-diimidazole ionophore was prepared. The newly synthesized calix[4]dicyano-diimidazole exhibited obvious absorbance enhancement at 284 nm in the presence of copper ions. At pH 6.8, the measuring range of the optode membrane for Cu 2+ ions was from 1.0 × 10 −8 to 1.0 × 10 −4 M with a detection limit of 7.0 × 10 −9 M. Furthermore, the response time of the proposed optical device was within 10 min. With the optimum condition described, the optical sensor revealed good selectivity toward Cu 2+ ions in comparison with common coexisting cations (Hg 2+ , Pb 2+ , Cd 2+ , Ni 2+ and Zn 2+ ). Finally, the reproducibility, regeneration, reversibility and repeatability of this optical sensor were discussed.

The potential energy curves and the spectroscopic constants of the ionic molecules CsLi+ and CsNa+ have been determined for the ground and the lowest 2Σ+, 2Π and 2Δ electronic states. Using an ab initio method, the calculation has been performed in a one active electron approach based on a non empirical pseudo-potentials with core valence effects taken into account through parameterized l-dependant polarization potentials. Numerous avoided crossing between electronic states of 2Σ+ and 2Π symmetries have been localised and analysed for the both ionic molecules. Their existences are related to the charge transfer process between the two ionic systems Cs+X and CsX+ (X = Li, Na). Furthermore, the transition dipole moment from the ground state X2Σ+ and the first excited state 22Σ+ to higher excited states have been determined for both CsLi+ and CsNa+ ionic systems. For our best knowledge, there are neither experimental nor theoretical works realised on these ionic molecules.

We have used electron paramagnetic resonance (EPR) spectroscopy for investigating the properties of spins, such as those carried by polarons which carry both spin and charge in poly (meta/para phenylene) PMPP: CdS doped Mn based nanocomposites. To identify the nature of paramagnetic species in PMPP matrix, we have studied the effect of different physical parameters. It was found that we are in presence of trapped polarons and localized spins which concentration has been estimated. Moreover, spin–spin and spin–lattice relaxation rates have been calculated. Then, we discussed the results of optical and EPR study on the hybrid nanocomposite (CdS nanostructures, doped with manganese (II) ions, incorporated in PMPP conjugated polymer matrix). The optical spectra of these nanocomposites were compared to the existing models of energy levels in quantum dots. Moreover, by the use of electronic paramagnetic resonance, conclusions about the location and the symmetry of Mn 2+ ions have been drawn. The nanocomposite energy gap is in the 3.2–3.3 eV range. The size of the nanoparticle is about 3.3 nm and Mn 2+ ions are located at or near the nanoparticle surface.

Luminescence characteristics of Er 3+ -activated, Yb 3+ -sensitised GeO 2 –Na 2 O–Nb 2 O 5 heavy metal germanate glasses have been investigated in the context of searching active media for laser devices. Optical absorption, emission spectra and decay time measurements have been performed at room temperature on these materials. Intense 1540 nm infrared fluorescence and visible emission bands at 533, 554, and 660 nm were observed under continuous wave excitation at 980 nm. An efficient energy transfer from Yb 3+ to Er 3+ ions, increasing as a function of Yb 3+ concentration, favours the Er 3+ 1.54 μm eye-safe laser emission in these materials. The power dependence study of the upconverted emissions gives evidence of a bi-photonic process. Moreover, the Yb 3+ codoping enhances the up-conversion efficiency. Decay time measurements have been examined in the purpose of elucidating the possible mechanisms involved in this process. The experimental results are in good agreement with an effective Yb 3+ -to-Er 3+ nonradiative energy transfer.

In this paper, the bacterial adhesion to hydrophilic glass and hydrophobic indium tin oxide (ITO) coated glass surfaces was investigated. The aim of this work was to examine the effect of the hydrophobicity of two bacterial strains ( Pseudomonas stutzeri PS, and Staphylococcus epidermidis SE) and substrata surfaces on the adhesion mechanism. The hydrophobicity of the surfaces of the bacterial strains as well as of the surfaces of the tested materials was characterized using the contact angle measurement via sessile drop technique. The water contact angle measurements of the intrinsic cell hydrophobicity showed that the PS strain is more hydrophobic ( θ = 40°) than SE strain ( θ = 21°). For both tested materials, this angle was 12° for glass surface and 84° for ITO-coated glass surface. Based on the thermodynamic approach, the Lifshitz van der Waals interaction free energy, the hydrophobic interaction free energy and the total interaction free energy between the bacteria and the substratum through the suspending medium were quantified. In order to verify the thermodynamic approach predictions of the bacterial adhesion on each substratum, adhesion tests were carried out for each bacteria/substratum combination. The results revealed that for both materials surfaces, the adhesion energy of the hydrophobic PS strain (26.1 mJ/m 2 for glass and − 3.8 mJ/m 2 for ITO-coated glass) is higher than that of SE strain (31.8 mJ/m 2 for glass and 14.3 mJ/m 2 for ITO-coated glass). For both bacterial strains, the effect of the hydrophobicity property of the substratum seems more important in the initial adhesion step. However, the second step of adhesion involves the biological approach, since a discrepancy was found between physicochemical theoretical approach and adhesion tests for SE strain.

We study the electrochemical response of a field effect capacitor composed by a porous silicon (PS)/silicon dioxide (SiO2) structure as transducer's surface and p-tert-butylcalix[6]arene molecules as a recognizing agent towards nickel ions. Silicon samples were electrochemically anodized in a hydrofluoric acid (HF) electrolyte leading to PS formation. SiO2 layers were obtained by anodic oxidation (AO) of PS in aqueous solution. Electrochemical measurements of the sensor with an Electrolyte/Insulator/Semiconductor (EIS) structure have been performed in the Capacitance/Voltage (C/V) mode. A comparative study of sensor responses depending on AO solutions is presented. We have observed a closer Nernstian response, of the coated and oxidized PS, to the Ni2+ ions that were anodically oxidized in a KNO3 (1 M) solution.

In this work, we investigate the effect of indium tin oxide (ITO) substrate cleaning on the surface properties. Wettability technique was used to measure the contact angle and the surface energy of the different treated ITO substrates. It is found that treatment with the methanol without dehydration gives the lowest water contact angle (most hydrophilic surface) and the highest surface energy compared to other solvents. This result was confirmed by impedance measurements performed on nematic liquid crystal cells with ITO electrodes. Indeed, we check the decrease of ionic entities in the interface ITO/liquid crystal. The polarity and dielectric parameters of the used solvents explain the obtained results.

New chromogenic calix[4]arene derivatives proved many applications in optical and electrical fields. Organic diodes formed by sandwiching azo-calix[4]arene layers between indium-thin oxide (ITO) and (Al) contacts have been elaborated and measured. In this paper, studies of devices by current–voltage characteristics I(V) and electrical impedance spectroscopy measurements in a wide frequency range have been reported. The electrical characteristics follow a space charge limited conduction behaviour (SCLC). Therefore, the Cole–Cole plots were modelled by an equivalent circuit. Relaxation processes have been identified too from the impedance spectroscopy. The optical excitation of the organic structure revealed enhancement in electrical properties.

Partially benzylated β-cyclodextrins (β-CDs) are deposited with no coupling agent on the silica surface of a wafer which was used as an electrolyte–insulator–semiconductor (EIS) heterostructure to detect cations in aqueous solution. The sensitivity of the EIS devices has been tested for Ca2+, Cu2+, K+ and heavy metal cations Pb2+ and Cd2+. The results showed a Nernstian response towards Pb2+ as found with β-cyclodextrins incorporated in gel membrane, with good selectivity. The benzylation of the β-cyclodextrins did not affect the complexation properties of the molecule. However, a considerable capacitive effect should be taken into account. The results were compared to a previous work where the β-CD molecules were fixed onto silica insulator surfaces obtained by means of either one of these two ways: chemically grafted to polymethyl-hydrosiloxanes (PMHS) chains, or physically entrapped in plasticized poly(vinyl chloride) (PVC).

The electronic structure and the spectroscopic constants of the low lying electronic states of the NaK+ ionic molecule have been determined through using an ab initio approach involving a non-empirical pseudopotential for the Na and K cores and core valence correlation correction. The potential energy of nearly 26 electronic states of 2Σ+, 2Π, and 2Δ symmetries has been calculated up to their dissociation limit Na(4d) + K+ and Na+ + K(6s). Their spectroscopic constants (Re, De, Te, ωe, ωeχe, and Be) are derived and compared with the few available theoretical studies. A good agreement has been found for the ground state and few excited states with previous works. New potential energy curves were presented, for the first time, for the higher excited states. Numerous avoided crossing between electronic states of 2Σ+, 2Π symmetries have been localized and analyzed. Their existences are related to the charge transfer between the two ionic molecules Na+K and NaK+. Furthermore, we have determined the transition dipole moments for several states and analyzed the avoided crossings related to charge transfer between alkaline atoms.

Investigations of the electrical characteristics of benzylated cyclodextrins (β-CDs (Bz)) diodes are reported. We present current–voltage characteristics and impedance spectroscopy measurements performed on partially benzylated cyclodextrins β-CDs (Bz) thin films in sandwich structures ITO/β-CDs (Bz)/Al. The static electrical characterizations show a space charge limited conduction (SCLC) and a conductivity with power low frequency behavior characteristic of a hopping transport in disordered materials. The impedance spectra can be discussed in terms of an equivalent circuit model designed as a parallel resistor RP and capacitor CP network in series with resistor RS. We extract numerical values of these parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution. We estimated from the capacitance voltage characteristic an acceptor concentration of about 1011 cm-3 due to trap states.

International audience; We have studied electrical properties of ITO/azo-calix[4]arene/Al diodes by means of current voltage measurement and impedance spectroscopy in a wide frequency range. The devices with an ITO/azo-calix[4]arene/Al structure could be modeled as a simple combination of resistors and capacitors. The impedance spectra can be discussed in terms of an equivalent circuit model designed as a parallel resistor R-p and capacitor C-p network in series with resistor R-s. We extract numerical values of these parameters by fitting experimental data. Relaxation processes have been identified too from the impedance spectroscopy. Their values deduced from fitting experimental data to the model have given a dielectric relaxation time in the ms range and an exponential trap distribution.

The adiabatic potential energy, the spectroscopic constants and the transition dipole moments of the lowest electronic states of the LiK+ molecule, dissociating into Li(2s, 2p, 3s, 3p, 3d, 4s, and 4p) + K+ and Li+ + K(4s, 4p, 5s, 3d, 5p, 4d, and 6s), have been investigated. We have used an ab initio approach involving a non-empirical pseudopotential for the Li (1s2) and K (1s22s22p63s23p6) cores and core valence correlation correction. A very good agreement has been obtained for the ground state for the spectroscopic constants with the available theoretical works. The transition dipole moment from X2Σ, 22Σ, 32Σ, and 42Σ states to higher excited states have been determined. Numerous avoided crossing between electronic states of 2Σ and 2Π symmetries, have been localised and analysed. Their existences are related to the charge transfer process between the two ionic systems Li+K and LiK+.