Gilles Marchand

Towards an Efficient Microsystem for the Real-Time Detection and Quantification of Mercury in Water Based on a Specifically Designed Fluorogenic Binary Task-Specific Ionic Liquid**

The control of water resources and the natural environment is a major current societal challenge that involves various partners at different levels (local government, water agencies, water treatment stations, citizens, consumer protection organizations, etc.). In this general context, facing the ecological hazards originating from the presence of heavymetal ions released in the environment (including water resources) is one of the important issues to address. Heavymetal ions such as mercury cause adverse environmental and health problems such as bioaccumulation by numerous organisms and severe physiological problems, including neurological, neuromuscular, or nephritic disorders. Indeed, mercury is considered the most toxic nonradioactive metal. Among the different forms (including the toxic organic derivative methylmercury), mercuric ions (Hg) are not only toxic but also highly water-soluble, making them bioavailable for humans and animals by ingestion of water. The toxicity associated with the bioavailability of Hg ions entails an increasing number of analyses to be carried out both on tap water and on water resources. Although laboratory analyses such as inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption or atomic emission spectroscopy are appropriate for precise quantitative measurements, they suffer from several drawbacks, including high cost and duration. Moreover the “in-lab” techniques cannot be readily used for real-time in situ analysis, which is required to monitor transient events such as release from thunderstorm overflow. Alternative selective Hg sensors have been reported based upon optical, electrochemical, electrical, or biological detection methods. These sensors allow in situ mercury monitoring, thus avoiding the use of laboratory analyses. However, most sensors are limited with respect to sensitivity or are not adapted for real-time monitoring of transient phenomena requiring high measurement repetition rates. This situation clearly calls for the development of efficient alternatives for in situ sensitive monitoring of water quality, which is subject to several official norms. To overcome this limitation, we herein propose a high-performance micro-total analysis system (mTAS), which is based on both the use of a novel selective and sensitive molecular fluorescent sensor in an ionic liquid phase and on liquid–liquid extraction, thus allowing concentrating extraction of the heavy-metal cation from a water phase. Several authors have reported the extraction of heavy metals with ionic liquids containing crown ethers with very high Nernst coefficients. Furthermore, the nonvolatility of ionic liquids enables their use in very low volume in open systems. One of the most recent developments in the field of ionic liquids is the use of task-specific ionic liquids (TSILs) or task-specific onium salts (TSOSs) as soluble supports, therefore expanding their potential applications far beyond those of conventional ionic liquids. TSILs retain all of the advantages of ionic liquids and can be used for liquid–liquid extraction with important benefits. Furthermore, TSILs (or TSOSs) can be dissolved in room-temperature ILs to give binary solutions combining all of the abovementioned benefits. Liquid–liquid extraction microsystems have been intensively developed during the last 10 years to extract, concentrate, and detect target molecules present in low concentrations in a liquid. Various solutions have been proposed to stabilize the interfaces, such as coflowing immiscible liquids separated by microridges, microporous membranes, or micropillars. However, classical organic solvents with poor Nernst coefficients were used in those microsystems, thus limiting their efficiency. In contrast, ionic liquids provide unique remarkable extraction abilities owing to their very high Nernst coefficient for metal-ion extraction. On the basis of the above analysis, we herein report the implementation and investigation of a novel and efficient microdevice for liquid– liquid extraction and sensing of mercury ions in water. The concept is based on an ionic liquid containing a TSOS, which combines fluorogenic and chelating properties to yield fluorescent-sensor ionic liquids (FSILs). Such immobilization of the metal binding unit in a hydrophobic IL would greatly [*] F. Loe-Mie, Dr. G. Marchand, Dr. J. Berthier, N. Sarrut, Dr. F. Vinet Department of Technology for Biology and Health CEA LETI-MINATEC, 17 rue des Martyrs, 38054 Grenoble (France) Fax: (+ 33)4-3878-5787 E-mail: gilles.marchand@cea.fr

Ferrocene and porphyrin monolayers on Si(100) surfaces: preparation and effect of linker length on electron transfer.

The missing link: Ferrocene and porphyrin monolayers are tethered on silicon surfaces with short (see picture, left) or long (right) linkers. Electron transfer to the silicon substrate is faster for monolayers with a short linker.Ferrocene and porphyrin derivatives are anchored on Si(100) surfaces through either a short two-carbon or a long 11-carbon linker. The two tether lengths are obtained by using two different grafting procedures: a single-step hydrosilylation is used for the short linker, whereas for the long linker a multistep process involving a 1,3-dipolar cycloaddition is conducted, which affords ferrocene-triazole-(CH(2))(11)-Si or Zn(porphyrin)-triazole-(CH(2))(11)-Si links to the surface. The modified surfaces are characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Cyclic voltammetry experiments show that the redox activity of the tethered ferrocene or porphyrin is maintained for both linker types. Microelectrode capacitor devices incorporating these modified Si(100) surfaces are designed, and their capacitance-voltage (C-V) and conductance-voltage (G-V) profiles are investigated. Capacitance and conductance peaks are observed, which indicates efficient charge transfer between the redox-active monolayers and the electrode surface. Slower electron transfer between the ferrocene or porphyrin monolayer and the electrode surface is observed for the longer linker, which suggests that by adjusting the linker length, the electrical properties of the device, such as charging and discharging kinetics and retention time, could be tuned.

Flexible sensors for real-time monitoring of moisture levels in wound dressings

OBJECTIVEnFew studies have investigated methods to monitor the moisture distribution and filling percentage of dressings during wound management. In this study, a new system allowing moisture monitoring across the wound dressing to be measured is examined.nnnMETHODnThe system is composed of a wound bed model with a fluid injection system to mimic exudate flow, a flexible sensor array and data acquisition software. The sensor is composed of 14 flexible electrode arrays, screen-printed on a flexible support and placed on the top of a wound dressing. The system is used to evaluate the performance of a foam-based dressing model.nnnRESULTSnDuring constant injection of fluid, the wound dressing absorbed moisture at the wound interface throughout the experiment, and expanded as the fluid spread from the wound bed to the edging areas of the foam. The in-time monitoring by the use of the screen-printed electrodes allowed a mapping of the dressing wet surface and estimation of the foam saturation (filling percentage) based on a simple acquisition method without the need to remove the dressing from the wound bed.nnnCONCLUSIONnThe findings of this study propose a non-invasive method to monitor the filling of the wound dressing and consequently, a potential solution for determining the optimal dressing change during wound management without causing irritation or further damage to the periwound skin.