A Highly Sensitive and Selective Optical Sensor for the On-Line Detection of Cesium in Water.

In this study, we have undertaken the development of two fluorescent sensors based on calixarene compounds for the purpose of detecting cesium in water. By introducing the sulfonate functional groups, we have considerably improved the water solubility of sensors, enabling complete dissolution of products in aqueous media and direct analysis of polluted water samples. Through rigorous experiments, we have demonstrated that the complexation of Cs+ ions with sensors 1 and 2 in water leads to a remarkable enhancement of fluorescence. This fluorescence enhancement serves as a reliable indication of cesium presence and allows for sensitive detection. To further advance the practical application of our sensors, we have successfully integrated calixarene sensors 1 and 2 into a microfluidic sensor chip. This integration has enabled real-time, on-line measurements and has resulted in the development of a portable detection device capable of detecting cesium ions in water samples at parts per billion (ppb) levels. This device holds great promise for environmental monitoring and assessment, providing a convenient and efficient solution for cesium detection. Our work represents a significant advancement in the field of cesium detection, displaying the efficacy of calixarene-based fluorescent sensors and their integration into microfluidic systems. The enhanced water solubility, fluorescence response, and portability of our detection device offers tremendous potential for applications in environmental monitoring, water quality assessment, and emergency response scenarios where rapid and accurate cesium detection is crucial.

Mercury detection in a microfluidic device by using a molecular sensor soluble in organoaqueous solvent.

A series of fluorescent sensor molecules based on a phosphane sulfide derivative that is soluble in an organoaqueous solvent were designed and synthesized. The structure of the fluorophore has been optimized in order to have the best compromise in terms of solubility and photophysical properties. The obtained properties are in full agreement with quantum chemical calculations. A fluorescent molecular sensor containing one polyoxoethylene group has been synthesized and an efficient quenching upon mercury complexation has been observed. Finally, this sensing molecule has been introduced in a microfluidic chip in which fluorescence detection has been integrated. An efficient fluorescence response was observed upon mercury addition.

A novel ruthenium(II) complex for two-photon absorption-based optical power limiting in the near-IR range.

In this article, the synthesis of a novel high-conjugated ligand and its corresponding Ru(II) complex PTFTF:Ru is reported, along with the linear and nonlinear optical characterizations. Two-photon absorption based optical power limiting properties (OPL), especially in the near infrared, are described and compared to those of the analogous complexes previously published. Combined with a preliminary theoretical approach, this allows us to highlight several key parameters for OPL optimization in such molecular systems and more particularly the spectral overlap between TPA and excited-state absorption.

Thermodynamics and kinetics of the complexation reaction of lead by calix-DANS4.

The thermodynamics and kinetics of the complexation reaction between lead ions and the fluorescent sensor Calix-DANS4 are determined to optimize the geometry of the microreactor used for the flow-injection analysis of lead and to tune the working conditions of this microdevice. Under our experimental conditions (pH 3.2, low concentration of Calix-DANS4) the 1:1 Pb(2+)-Calix-DANS4 complex is predominantly formed with a high stability constant (log K(1:1)=6.82) and a slow second-order rate constant (k=9.4×10(4) L mol(-1) s(-1)). Due to this sluggish complexation reaction, the microchannel length must be longer than 130 mm and the flow rate lower than 0.25 mL h(-1) to have an almost complete reaction at the output of the microchannel and a high sensitivity for the heavy metal detection. After determination of the values of the reaction times in our different microdevices, it is possible to simulate the calibration curves for the fluorimetric detection of lead under different conditions. An original method is also presented to determine mixing times in microreactors.

Pi-stacking functionalization of carbon nanotubes through micelle swelling.

We report on a new, original and efficient method for pi-stacking functionalization of single-wall carbon nanotubes. This method is applied to the synthesis of a high-yield light-harvesting system combining single-wall carbon nanotubes and porphyrin molecules. We developed a micelle-swelling technique that leads to controlled and stable complexes presenting an efficient energy transfer. We demonstrate the key role of the organic solvent in the functionalization mechanism. By swelling the micelles, the solvent helps the non-water-soluble porphyrins to reach the micelle core and allows a strong enhancement of the interaction between porphyrins and nanotubes. This technique opens new avenues for the functionalization of carbon nanostructures.

Sensitized emission of luminescent lanthanide complexes based on a phosphane oxide derivative.

The photophysical properties of a complex based on diphenylphosphanoethane (DPPE) fluorescent ligands linked to a europium ion have been investigated by different spectroscopic methods. Upon complexation with europium, the interaction of the phosphane oxide group with europium leads to a red shift of the absorption spectrum and a strong quenching of the ligand emission. The typical sensitized emission of Eu(3+) is observed upon excitation of the ligand with a fluorescence quantum yield of 1%. Time-resolved absorption and emission experiments have been performed in order to investigate the photophysical mechanism involved in this complex. Photophysical studies show that an energy-transfer mechanism occurs from both the first excited singlet and triplet states of the ligand, and the population of the europium ion to the (5)D(1) state takes place, from which the (5)D(0) state is populated. Additionally, electron transfer from the excited singlet state of the ligand to the europium ion appears as a very efficient process.

Fluorimetric lead detection in a microfluidic device.

A microfabricated device has been developed for the selective detection of lead in water. It is based on the use of a selective and sensitive fluorescent molecular sensor for lead (Calix-DANS4) which contains a calix[4]arene bearing four dansyl groups. The microchip-based lead sensor contains a Y-shape microchannel equipped with a passive mixer and moulded on a glass substrate. An optimization of the microcircuit length has been performed in order to have a full complexation of the Calix-DANS4. The detection is performed by using a configuration in which the sensing molecules are excited by two optical fibres, each one connected to a 365 nm UV LED, and the light collection is made by another optical fibre with a photomultiplier. By using this configuration we have shown the possibility to detect lead with a detection limit of 5 ppb. The effect of interfering cations such as calcium has been evaluated. The obtained measurements have been validated by an alternative method (ASV).

Carbon nanotube-acridine nanohybrids: spectroscopic characterization of photoinduced electron transfer.

Single-walled carbon nanotubes (NT) were covalently functionalized with either 9-phenyl acridine (PhA) or 10-methyl-9-phenyl acridinium (PhMeA(+)). Absorption and fluorescence properties of acridine derivatives tethered to the nanotubes were studied in homogeneous dispersions. Exciplex emission was observed for NT functionalized with 9-phenylacridine. This phenomenon was attributed to an "intramolecular" interaction between excited phenyl acridine and carbon nanotubes. Interestingly, reverse photoinduced electron transfer from the nanotube to 10-methyl-9-phenylacridinium was detected for the NT-PhMeA(+) nanohybrid. This electron transfer led to a strong quenching of the acridinium fluorescence and to the formation of a metastable acridine radical. Evidence for the formation of this radical was obtained by ESR studies.

A novel microfluidic flow-injection analysis device with fluorescence detection for cation sensing. Application to potassium.

A microfabricated device has been developed for fluorimetric detection of potassium ions without previous separation. It is based on use of a fluorescent molecular sensor, calix-bodipy, specially designed to be sensitive to and selective for the target ion. The device is essentially made of a Y-shape microchannel moulded in PDMS fixed on a glass substrate. A passive mixer is used for mixing the reactant and the analyte. The optical detection arrangement uses two optical fibres, one for excitation by a light-emitting diode, the other for collection of the fluorescence. This system enabled the flow-injection analysis of the concentration of potassium ions in aqueous solutions with a detection limit of 0.5 mmol L(-1) and without interference with sodium ions. A calibration plot was constructed using potassium standard solutions in the range 0-16 mmol L(-1), and was used for the determination of the potassium content of a pharmaceutical pill. Figure Photography of the microfluidic channel showing the ridges in the PDMS substrate at the top of the channel.

Photophysical properties of glucoconjugated chlorins and porphyrins and their associations with cyclodextrins.

Glucoconjugated analogues of the meta-hydroxyphenyl porphyrin (m-THPP) and meta-hydroxyphenyl chlorin (m-THPC) has been recently synthesized. The characteristics of their triplet states have been determined with regard to their involvement in the photodynamic (PDT) efficiency. In the case of porphyrin derivatives, triplet quantum yields (Phi(T)) were ranging from 0.42 to 0.55 and triplet life times (tau(T)) from 1 to 5 micros. High reaction rate constants (k(q)) with molecular oxygen (k(q): 1.2-1.6 x 10(9)s(-1)) have been found. The triplet lifetimes of chlorin derivatives were about four times higher than those of porphyrins whereas the Phi(T) and k(q) values remained quite similar. Singlet oxygen yields of glucosylated and non-glucosylated porphyrins and chlorins were not significantly different within experimental errors (Phi(Delta)((1)O(2)): 0.41-0.58). Furthermore, it has been shown that glucoconjugated photosensitizers could undergo associations with the methyl-beta-cyclodextrin (Me-beta-CD) which exhibit high triplet lifetimes and singlet oxygen yields ranging from 0.27 to 0.48.

Versatile synthesis of small NLO-active molecules forming amorphous materials with spontaneous second-order NLO response.

A novel synthetic approach to a series of bulky triarylamines substituted by various electron-withdrawing groups and forming amorphous materials is presented. Under vacuum evaporation, thin films with high optical quality are obtained and exhibit spontaneous second-order nonlinear optical activity. This unprecedented result is likely due to subtle balance between strong dipole-dipole interactions and steric crowding causing self-assembly and noncentrosymmetric local ordering, stable up to one year.

Photochromic compounds as optical limiters in the nanosecond time range: the example of mercury dithizonate complex.

Although being an efficient photochromic compound which absorbs in the blue in its stable form and in the orange in its photoactivated form, the mercury dithizonate complex is shown to be a poor optical limiter for nanosecond laser pulses at the wavelengths where both isomers absorb. Optical limiting effect, which is a consequence of reverse saturable absorption due to the photoactivated form, is demonstrated to be weak because of the back photobleaching of this form, which is important all the more as the laser intensity is high. Numerical integration of the spatiotemporal evolution of the laser beam intensity across the solution helps the understanding of the respective roles of the laser fluence and pulse duration. Finally, we draw the conclusion that photochromic compounds can only be used as optical limiters if the time constant for the back photochemical reaction is slow compared to the pulse duration.