Influence of etching and surface functionalization on the properties of luminescence silicon quantum dots
A. Gupta, A.S.G. Khalil, M. Winterer, H. Wiggers
University of Duisburg-Essen, DE
Keywords: surface functionalization, FTIR, Photoluminescence, stabilty of dispersion, zeta potential
Abstract:The light emission from silicon quantum dots (Si-QDs) has sparked a great interest in their research due to the possibility of constructing optoelectronic devices, full color displays and optical sensors based on silicon. We present an efficient method of producing macroscopic quantity of Si-QDs with bright photoluminescence (PL). Si-QDs were synthesized in a microwave plasma reactor by pyrolysis of silane (SiH4). After a surface etching of as-synthesized Si-QDs with hydrofluoric acid (HF) the Si-QDs are passivated by covalent attachment of organic molecules onto their surface via thermally induced hydrosilylation. The functionalized Si-QDs show a slight shift in luminescence compared to the freshly etched samples and exhibit high stability in air as well as a stable PL emission for months. The stability of Si-QDs in dispersion media is essential for their use in drug delivery applications and printable devices. The stability of as-prepared and functionalized Si-QDs in aqueous and non-aqueous dispersions has been investigated. The variation of zeta potential as a function of pH of the Si-QDs dispersed in aqueous solution has been studied. The Si-QDs show high zeta potential values within pH= 6.5-8.5. In addition, the Si-QDs do not show any isoelectric point in the pH range studied. The influence of the addition of new stabilizers on the stability of Si-QDs is currently under investigation. The preparation of stable dispersions of the Si-QDs will give the opportunity to fabricate films for different applications using ink-jet printing.