Naël ZRAN, Julie FAULEAU, Barthélemy GODIN, Haad BESSBOUSSE, Marie-Claude CLOCHARD et Travis L. WADE
En collaboration avec Iris NADHAKUMAR, University of Southampton, UK
En collaboration avec Murat BARSBAY, Hacettepe University, Ankara, Turquie
European and national regulations push towards real-time, on-site or in situ analyses to improve the reliability of monitoring regarding the representatively of sampling and to obtain faster information. For heavy-metals, tolerable limits are now in the very low to sub μg/L range. This requires fast, portable, low-cost, environmentally friendly and sensitive instruments that are capable of detecting and quantifing heavy-metal concentrations in different types of water; however, few options are readily available.
We have invented 3-D nanostructured membranes comprised of functionalized nano-cylinders acting as metal-ion traps  . The trapping capacity is very high leading to very sensitive sensors and the membranes passively adsorb ions for in situ sampling. The electrode is based on track-etched poly(acrylic acid) (PAA) functionalized nanoporous poly(vinylidene fluoride) (Béta-PVDF) membranes with porous gold electrodes on each side that function as working and counter electrodes for voltammetry. Béta-PVDF is a very durable material; it is nontoxic, bio-compatible and recyclable.
These 3-D nano-structured membrane sensors are comprised of functionalized nano-cylinders acting as metal-ion traps (five patents). The project has been financed by the Triangle de la Physique, OSEO Ils de France, C-nano and the ECOLE Polytechnique Department of Physics. The sensors have been compensated by two prizes: POLLUTEC 2012 Analyses-Mesure and a valorisation award to Haad Bessbousse OSEO 2012.
The nanopores are formed by heavy ion irradiation and chemical etching. The heavy ion irradiation produces damage tracks in the form of radicals from broken carbon-carbon bonds. These radicals are very stable in Béta-PVDF due the crystalline nature of the polymer. The radical tracks are chemically etched to reveal nanopore channels and the channel diameters are proportional to the etching time. After the etching; however, there are still radicals within the pores. These remaining radicals can be reacted with different monomers, such as acrylic acid (AA) or 4-vinyl pyridine (4-VP) to impart chemical functionalization to the nanopore interior without blocking the pores. Other complexing polymers can also be grafted inside the membranes.
Irradiation at GANIL (CIMAP, Caen FRANCE), etched and functionalized at the LSI.
The functionalized nanoporous Béta-PVDF membranes are then transformed into electrodes by the deposition of a thin gold (or other metal) layer onto both sides of the membrane. The metallic layer is thin enough (35 nm) that is does not completely cover the pores.
35 nm of gold sputter on each side through a mask.
When the electrodes are immersed in a liquid they can selectively absorb certain ions, such as Cu2+ and Pb2+ or Hg2+, depending on their functionalization by passive sampling. They can then be removed, rinsed and placed in an electrochemical cell for electrochemical analysis using anodic stripping voltammetry (ASV).
In situ adsorption with electrochemical analysis by ASV.
- in situ, portable
- easy fast analysis
- very sensitive
 H. Bessbousse, I. Nandhakumar, M. Decker, M. Barsbay, O. Cuscito, D. Lairez, M.-C. Clochard, T. L. Wade, Analytical Methods 2011 V3(6): p1351
 M. Barsbay, O. Güven, H. Bessbousse, T. L. Wade, F. Beuneu, M.-C. Clochard, J. of Membrane Science 2013 V445: p135