High photoluminescence quantum yield of TiO₂ nanocrystals prepared using an alcohothermal method

Abstract

Highly dispersible TiO2 nanocrystals (approximately 6 nm) were prepared by an alcohothermal method. A strong and stable photoluminescence emission with a maximum at 450 nm was observed in the original TiO2 nanocrystals colloid. Compared with the emission from quinine sulphate in 0.05 mol/L sulphuric acid, the emission quantum yield of TiO2 nanocrystals was determined to be about 0.20, which was much higher than the values (0.002 and 0.001) reported in previous studies. The fluorescence micrograph of TiO2 nanocrystals encapsulated in lipsomes shows that TiO2 nanocrystals prepared in such a way have potential application as a fluorescence probe in biological imaging. Research on the luminescence mechanism indicates that the surface state and extent of crystallization of the TiO2 nanocrystals are crucial factors in the high photoluminescence quantum yield obtained in this study.

Chiral and Luminescent TiO2 Nanoparticles

“…The quantum yield of the TiO 2 nanoparticles was determined to be 3.5% in THF solution when excited at 261 nm and was determined by the relative approach, using quinine sulfate dihydrate dye in 0.105 m HClO 4 in water as our standard which has a quantum yield of 60.9% . This quantum yield compares favorably with examples in literature measured at room temperature which range generally from 1.6 to 0.25 and even as low as 0.05%, though a single report does exist claiming quantum yields up to 20% …”

“…The origin of the longer wavelength absorption (past 400 nm), is assigned as occurring due to a combination of scattering and interband gap states. We have assigned the 265 nm peak to a quantum confined nanostructure of TiO 2 indicating that at least one dimension of our particles is on the order of 1–10 nm and therefore comparable to the Bohr radius of TiO 2 which is 1.5 nm…”

TiO2/porous silicon nanocomposite passivation coating for mc-Si wafers

“…Two additional peaks have been detected after the deposition of TiO 2 (as compared to PS). The UV PL emission peak at 370 nm (3.35 eV) is generally attributed to the TiO 2 band-to-band recombination, because it is near the luminescence bandedge [16][17][18][19][20][21]. Blue emission from dispersible anatase TiO 2 nanocrystals corresponds to indirect transitions (3.05 eV) and to oxygen vacancies [22,23].…”

Structural and luminescence properties of Y2‐xGeMoO8:REx (RE = Eu, Tb) phosphors

“…shows a gradual increment in the intensity of the diffraction peaks, for instance the {112} index. It is considered that at a lower temperature, here 1000°C, the growth of small and individual subcrystallites through oriented attachment or the Oswald ripening mechanism to form large crystals is slowed, resulting in a smaller crystal size and poorer crystallinity (14,15). By contrast, the growth rate can be accelerated at higher temperatures, producing larger crystals with better crystallinity.…”