From the view point of practical application, one thorny problem in organic light emitting diode (OLED) devices is how to protect the inner materials from being eroded by oxygen and moisture, and to undertake sufficient long-term stability. Alq₃ is the earliest and widely used organometallic material as an electron transport layer and light emitting layer in OLED, undoubtedly, improving its photochemical stability via coating it with materials that possess anti-oxygen and anti-water characters is one of cost-effective ways. Motivated by this, here, we demonstrate one pot synthesis of Alq₃@SiO₂ with uniform SiO₂ covering. To obtain the optimized core-shell Alq₃@SiO₂ particle, a mixture of 8-hydroxyquinoline (6 mmol), 1 mL Et₃N and 2 mL deionized water was dissolved in 120 mL ethanol and then heated to 70 ℃, a solution of Al₂(SO₄)₃·18H₂O (1 mmol) in 5 mL water and a solution of tetraethylorthosilicate (TEOS) (2 mmol) in 5 mL ethanol were added dropwise at the same time, respectively. The mixture was allowed to react at 70 ℃ for about 5 h. Then, a green precipitate was obtained, and purified by washing with water and ethanol. The scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to characterize the morphology of the as-synthesized Alq₃@SiO₂ particles, which exhibited better results than previous reported. From the measurement of UV-Vis and PL spectra we can see the Alq₃@SiO₂ we have produced exhibited similar absorption and emission profile compared to pristine Alq₃, which is beneficial for future application in OLED because it is almost not change the optical property of Alq₃. The prepared principle of Alq₃@SiO₂ can be assigned to the plausible Cage Effect of Et₃N embraced Lewis acid Alq₃, and a further Et₃N catalytic hydrolysis of TEOS to produce SiO₂ on the surface of formed Alq₃. Note that Et₃N used in this case is also acted as Alq₃ morphology protective agent during TEOS hydrolysis. This work provides a facile and large scale preparation of Alq₃@SiO₂ for future improving the long-term stability of OLED devices.

Key words: one pot synthesis, Alq₃@SiO₂, Alq₃, TEOS, Et₃N