Luminescent colloidal silicon particles

• Published in: Chemical physics letters 1994-04, Vol.221 (5), p.363-367
• Main Authors: Fojtik, Anton, Henglein, Arnim
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/0009-2614(94)00271-1

Crystalline silicon particles, which are coated by an oxide layer, are prepared by combustion of silane. Red or orange luminescence is activated by etching them in a 1:1 cyclohexane—propanol-2 suspension by aqueous hydrogen fluoride in the presence of air. The temporal changes in the luminescence intensity of the suspension (several days) are described. When a suspension of luminescent particles in cyclohexane is mixed with polar solvents such as alcohol, ether and chloroform, a more or less quenching of the luminescence (depending on the nature of the added solvent) occurs. Mixing with non-polar solvent such as carbon tetrachloride does not lead to quenching. Triethylamine and ammonia quench the luminescence extremely effectively. Sulfuric acid also quenches. The particles migrate in an electric field in different directions depending on the chemical surface treatment. It is concluded that luminescence occurs when the particles carry only a few oxidized centers on the surface, and the protonation state of these centers strongly affects the luminescence.