Silicon nanoparticles as a versatile luminescent tool

JUAN JOSÉ ROMERO; HERNÁN B. RODRÍGUEZ; MÓNICA C. GONZALEZ

Santa Fé

Congreso; Congreso Internacional de Metalurgia y Materiales 2014 / SAM-CONAMET / IBEROMAT / MATERIA; 2014

Silicon nanoparticles of 1?5 nm size (SiNPs) have received great attention as they are biocompatible, exhibit visible photoluminescence and produce reactive oxygen species upon UV-visible or X-ray excitation, making them potential candidates for fluorescence imaging, photodynamic therapy and radiotherapy of cancer. Moreover, combination of SiNPs with organic chromophores and/or metal nanoparticles may induce important changes in their photochemical behaviour, allowing the design of versatile systems with well-defined properties. In the present work, SiNPs synthesized by different routes were characterized, paying special attention to their photophysical and singlet oxygen generation properties. SiNPs were synthesized using a variety of techniques, briefly: electrochemical etching of Si wafers, chemical etching of porous Si using HF, reduction of Si halides in presence of micelles, and oxidation of Metal Silicides. The NPs obtained were further derivatized with 2-propenyl-amine, and characterized using X-Ray Photoelectron Spectroscopy, High Resolution Transmission Electron Microscopy, Fourier Transform Infrared Spectroscopy, UV-Vis absorption Spectroscopy, Fluorescence Spectroscopy, Time Correlated Single Photon Counting and Singlet Oxygen Phosphorescence Detection. Depending on the synthetic route, SiNPs with different sizes and crystallinity were obtained. Conversely, it was found that the excitation-emission matrix shape and luminescence decay times of oxidized SiNPs < 3 nm-size, with surface Si-O-Si structures, do not depend on the particle crystalline structure, neither on size, nor on further organic capping. This observation has important consequences for potential technological applications, as the proper synthetic route may be selected on costs and availability of reactants and equipment [1]. Current experiments follow the coupling of SiNPs with silver nanoparticles, in order to explore metal-enhanced photochemistry [2]. [1] Romero, J. J.; Llansola-Portolés, M. J.; Dell?Arciprete, M. L.; Rodríguez, H. B.; Moore, A. L.; Gonzalez, M. C. Chem. Mater., 2013, 25, 3488?3498. [2] Lakowicz, J. R. Anal. Biochem., 2005, 337, 171?194. Acknowledgments J.J.R. thanks CONICET, Argentina, for his doctoral fellowships. M.C.G. and H.B.R. are research members of CONICET. This research was supported by grant PIP112-200801-00356 from CONICET.