Novel core–shell (TiO2@Silica) nanoparticles for scattering medium in a random laser: higher efficiency, lower laser threshold and lower photodegradation

Abstract

There has been growing interest in scattering media in recent years, due to their potential applications as solar collectors, photocatalyzers, random lasers and other novel optical devices. Here, we have introduced a novel core-shell scattering medium for a random laser composed of TiO2@Silica nanoparticles. Higher efficiency, lower laser threshold and long photobleaching lifetime in random lasers were demonstrated. This has introduced a new method or parameter (fraction of absorbed pumping), which opens a new avenue to characterize and study the scattering media. Optical chemical and colloidal stabilities were combined by coating a suitable silica shell onto TiO2 nanoparticles.

Observation of photonic paramagnetic to spin-glass transition in a specially designed TiO_2 particle-based dye-colloidal random laser

“…Then, a photocatalytic process is started leading to fast dye degradation [24]. Attempts to minimize the photodegradation were made using scatterer particles based on materials with large energy bandgap [21][22][23]. Indeed, silica particles, which have energy bandgap of ~ 5.0 eV and refractive index of ~ 1.7 in the visible range, have been used and lower photodegradation was observed [21][22][23].…”

“…Attempts to minimize the photodegradation were made using scatterer particles based on materials with large energy bandgap [21][22][23]. Indeed, silica particles, which have energy bandgap of ~ 5.0 eV and refractive index of ~ 1.7 in the visible range, have been used and lower photodegradation was observed [21][22][23]. However, two other important points neglected by most of researchers are the particles precipitation and the chemical bonding between the particles and the cuvette walls that contribute to reduce the efficiency and lifetime of the RLs.…”

Dynamic random lasing in silica aerogel doped with rhodamine 6G

“…Additionally, a decrease of R6G absorption is expected above RL threshold, which has been observed in previous works. 11,23 The result of the measured absorption coefficient as function of wavelength is seen in Fig. 1e.…”

Anomalous transport of light at the phase transition to localization: strong dependence with incident angle

“…By using a Stöber method [25,26], TiO2 NPs were coated with a homogeneous silica shell of ~40 nm thickness. The silica coating with thicknesses around or above 40 nm prevents the "optical" junction of the TiO2 scattering surfaces (steric "optical" effect) [27], decreasing the near-field coupling that could hamper localization [28]. We called this property optical colloidal stability [27].…”