Direct visualization of nanoparticles loaded in a nanoporous silicon matrix
C. Chiappini, E. Tasciotti, X. Liu, D. Fine, M. Ferrari
The University of Texas at Austin, US
Keywords: porous silicon, TEM, tomography, Q-dots, embedding, mapping EDS
Abstract:To date the proof of the penetration of nanoparticles within the matrix of porous silicon has never been obtained by direct visualization but rather indirectly observing the properties of the resulting system. Direct observation of the nanoparticles within the matrix adds significant information on the behavior of the system and opens new avenues for the explanation of phenomena occurring at the nanoscale. In this work we prove the ability to directly visualize, localize three-dimensionally and provide an elemental map of nanoparticles within a pSi matrix. Porous silicon particles of different average pore size are infused with 15nm diameter Cd-Se Q-dots. Microtomed samples are analyzed by Electron Microscopy. HAADF-STEM shows Q-dots as bright spots within the darker silicon matrix. STEM-mapping EDS shows co-localization of the Cd-Se signals with HAADF spots, indicating a way to discriminate simultaneously loaded nanoparticles. Computerized TEM tomography shows the three-dimensional localization and spatial organization of the nanoparticles within the matrix. Direct visualization provides access information to the density gradient of nanoparticles within the matrix, their aggregation and their packing capability as a function of pore size, co-loading, chemical/physical functionalization and loading procedure and provides key information for the optimization of the nanosystem by maximizing its performance.