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This presentation focuses on the synthesis and characterization of luminescent silicon nanoparticles that have potential as components of hybrid inorganic/organic materials for photonic and biophotonic applications. In our lab, silicon nanoparticles with bright visible photoluminescence are being prepared by a new combined vapor-phase and solution-phase process, using only inexpensive commodity chemicals. CO2 laser-induced pyrolysis of silane is used to produce Si nanoparticles at high rates (20 to 200 mg/hour). Particles with an average diameter as small as 5 nm can be prepared directly by this method. Etching these particles with mixtures of hydrofluoric acid (HF) and nitric acid (HNO3) reduces the size and passivates the surface of these particles such that they exhibit bright visible luminescence at room temperature. The wavelength of maximum photoluminescence (PL) intensity can be controlled from above 800 nm to below 500 nm by controlling the etching time and conditions. Particles with blue and green emission are prepared by rapid thermal oxidation of orange-emitting particles. These particles have exciting potential applications in optoelectronics, display technology, chemical sensing, biological imaging, and other areas. The availability of relatively large quantities of these particles is allowing us to begin to functionalize particles for these applications, as well as to study the optical, electronic, and surface chemical properties of them. All of these potential applications require inorganic/organic hybrid materials, in the sense that the nanoparticles must have their surfaces coated with organic molecules that mediate the interaction of the particles with the polymeric or biological host matrix. The particle synthesis methods, photoluminescence measurements on the particles, the stability of the photoluminescence properties with time, chemical quenching of photoluminescence, and functionalization of the particles for incorporation into different organic matrices or for specific interaction with small molecules or biomolecules are
discussed in the context of applications to photonics and biophotonics.
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