Blue –emitting silicon nanoparticles: photophysical properties.

MANUEL JOSÉ LLANSOLA PORTOLÉS; FELIPE RODRIGUEZ NIETO; DELIA B. SORIA; JAVIER AMALVY; DANIEL O. MÁRTIRE; MÓNICA KOTLER; MÓNICA C. GONZALEZ

J.Phys.Chem.C

ACS

Año: 2009 vol. 113 p. 13694 - 13702

1932-7455

Summary Silicon nanoparticles with strong blue photoluminescence were synthesized by anodic oxidation of silicon wafers and ultrasonically removed under N2 atmosphere in organic solvents to produce colloids. Fast thermal treatment leads to the formation of colloidal Si particles of 3 ± 1 nm diameter size, which upon excitation with 340 – 380 nm light exhibited room temperature luminescence in the range from 400 to 500. The emission and the one- and two-photon excitation spectra of the particles are not sensitive to surface functionalization with methylmethacrylate. However, the derivatized particles in toluene suspensions show higher quantum yields in air saturated suspensions (20%) than “naked” particles (9%), as well as higher stability in dispersion and stable emission in ambient air for up to 4 months. FTIR spectra show that the particles are oxygen passivated, as important absorption due to Si-OH and Si-O-Si vibrations is observed. The involvement of vibrations in the emission and excitation spectra suggests that the blue luminescence is related to the presence of XXOH groups. However, the mechanism of blue emission from these particles remains an open question to be addressed. Both, the information obtained from one-photon excitation experiments (emission and excitation spectra, photoluminescence quantum yields, luminescence decay lifetimes and anisotropy correlation lifetimes), and from two-photon excitation fluorescence correlation spectroscopy (brightness and diffusion coefficients) show that blue emitting particles are monodisperse, ball-shaped and of high-quality surface passivation. The nanoparticles could hold great potential as quantum dots for applications as luminescence sensors in biology and environmental science.