Effect of water and UV passivation on the luminescence of suspensions of silicon quantum dots
This article presents the evolution of the photo-luminescence (PL) of silicon quantum dots (QDs) with an average diameter of 5–6 nm dispersed in alcohol under different conditions. Two samples were considered after alcohol dispersion: freshly synthesized (kept in air for 2 days) QDs which do not exhibit luminescence and air-aged (kept in air for 2 years) QDs exhibiting red-IR luminescence. Experiments performed with addition of a small volume of water, followed by heating for different times showed that the oxidation occurs gradually until transforming totally the initial material in SiO2. The oxidation process does not enable the appearance of PL from the Si core for dispersed non-aged powders, while it results in a blue shift of the PL maximum intensity for the aged ones. The results obtained after UV illumination clearly indicate an effect of the UV irradiation on the luminescence of QDs dispersed in aqueous environment, and the treatments with acidic water lead to the conclusion of a possible enhancement of the PL by hydrogen passivation of the non-radiative defects. This result should be taken into account for post-production treatments and applications, more particularly, considering a controlled and safe use of luminescent Si QDs.
KeywordsSilicon Nanoparticles Quantum dot Passivation Luminescence Aqueous suspensions Environment EHS
- Fujioka K, Hiruoka M, Sato K, Manabe N, Miyasaka R, Hanada S, Hoshino A, Tilley RD, Manome Y, Hirakuri K, Yamamoto K (2008) Luminescent passive-oxidized silicon quantum dots as biological staining labels and their cytotoxicity effects at high concentration. Nanotechnology 19:415102CrossRefGoogle Scholar
- Meier C, Gondorf A, Lüttjohann S, Lorke A, Wiggers H (2007) Silicon nanoparticles: absorption, emission, and nature of the electronic bandgap. J Appl Phys 101:103112 1–8Google Scholar
- Robertson J (1988) Electronic structure of defects in amorphous SiO2. In: Devine RAB (ed) The physics and technology of amorphous SiO2. Plenum, New York, pp 91–117Google Scholar
- Rogach A (ed) (2008) Semiconductor nanocrystal quantum dots: synthesis, assembly, spectroscopy and applications. Berlin: Springer PublicationsGoogle Scholar
- Veinot J (2006) Synthesis, surface functionalization, and properties of freestanding silicon nanocrystals. Chem Commun 4160–4168Google Scholar