Development of partially oxidized blue-emitting silicon nanoparticles.

M.J. LLANSOLA PORTOLÉS; F.J. RODRÍGUEZ NIETO; B. SORIA,; D.O. MÁRTIRE; M.L. KOTLER; M. C. GONZALEZ

Toledo, España

Congreso; International Conference on Photochemistry 2009; 2009

Universidad de Toledo

Silicon nanoparticles with strong blue photoluminescence were synthesized byanodic oxidation of silicon wafers and ultrasonically removed under N2 atmosphere inorganic solvents to produce colloids. Fast thermal treatment leads to the formation ofcolloidal Si particles of 3 to 1 nm diameter size, which upon excitation with 340 – 380 nmlight exhibited room temperature luminescence in the range from 400 to 500 nm withquantum yield of around 30% in toluene. The luminescence properties of the particles arenot sensitive to surface functionalization with either methylmethacrylate or methanol.However, the derivatized particles show higher stability in dispersion and their emission isstable in ambient air for up to 4 months.FTIR spectra show that the particles are highly oxygen passivated, as importantabsorption due to Si-OH and Si-O-Si vibrations is observed. The involvement of vibrationsin the emission and excitation spectra suggests that the blue luminescence is related to thepresence of HO groups. However, the mechanism of blue emission from these particlesremains an open question to be addressed. Both, the information obtained from one-photonexcitation experiments (emission and excitation spectra, photoluminescence quantum yields,luminescence decay lifetimes and anisotropy correlation lifetimes), and from two-photonexcitation fluorescence correlation spectroscopy (brightness and diffusion coefficients)show that blue emitting particles are monodisperse, ball-shaped and of high-quality surfacepassivation.Acknowledgements: The frequency domain fluorescence and anisotropy measurements,and the fluorescence correlation spectroscopy experiments were performed at theLaboratory for Fluorescence Dynamics (LFD) at the University of California, Irvine (UCI).The LFD is supported jointly by the National Center for Research Resources of the NationalInstitutes of Health (PHS 5 P41-RR003155) and UCI.