Hybrid Porous Silicon- Rhodamine B Derivative Nanostructures as Chemical Sensor for Hg(II) Detection

In this work we propose a new method to produce a fluorescent chemical sensor for mercury detection (Hg(II)). This device is mainly based on the optical properties of porous silicon nanostructures (PSi) [1] coupled with the fluorescent properties of    Rhodamine B [2] (Rh-urea-Ph-urea-Si) ligand derivative, which is covalently linked to PSi acting as receptor of metal ions. The Rh-urea-Ph-urea-Si (Ph=Phenil) compound was synthesized and its complexing ability was studied in liquid phase and solid by fluorescence spectrometry. The results showed that the fluorescence response of the metallic complex is metal concentration dependent. If the Hg(II) concentration increases, the florescence intensity also increases to reach the saturation point of the fluorophore. The electrochemical etching of crystalline silicon wafer [3] produced the PSi transducers, which in turn were functionalized with the organic receptors. The ligand infiltration into the PSi matrix and the metal coordination on the hybrid substrate were evaluated by specular reflectance, infrared and fluorescence spectroscopy, and SEM. Fluorescence microscopy confirmed the qualitative detection of Hg(II) ions due to the increase of the  fluorescence observed after metal capture. The changes in electrical impedance upon porous silicon samples before and after the chemical modification, allowed us to obtain the approximate surface area of the porous devices. During the presentation of this work, the Hg (II) detection through voltammetric techniques will be discussed.

 Acknowledgements.

 This work was supported by the CONACYT, Project No. CB-153161 and 169634. P Mayela De la Cruz thanks the

CONACYT Scholarship: 237466. We acknowledge to Olga Dávalos Montoya for FTIR support and Prof. Jaime Ruiz for the facilities provided for the use of the fluorescent microscope.

References.

[1] A. Melek, D. Wissem, M. Ghrib, C. Radhouane, Ezzaouia. Journal of Luminescence. 132 (2012) 277-281.

[2] Zhisheng Wu, Xuanjun Wu, Yuhui Yang, Ting-bin Wen, Shoufa Han, Bioorganic & Medicinal Chemistry Letters. 22 (2012) 6358–6361.

[3] G. Palestino, M. Martin, V. Agarwal, R. Legros, T. Cloitre, László Zimanyi, C. Gergely, Phys. Status Solidi C. 6(7) (2009) 1624-1628