Defensin Expression in Tears in Response to Ocular Surface Surgery and Corneal Wounding

Abstract

The optical behaviour of a hitherto unexplored compound GdScO3 is investigated. The orthorhombic GdScO3 was obtained by gel combustion synthesis which yielded phase pure product at temperatures as low as 650 °C. Despite the absence of any activator, undoped GdScO3 showed distinct excitation and emission spectra attributed to various shallow and deep defects present in the system. Annealing temperature altered the emission characteristics which exhibited prevalence of more deep defects on increasing the temperature. An efficient host to activator energy transfer was observed in the Eu3+ and Tb3+-doped GdScO3. However, an incomplete energy transfer to Dy3+ resulted in an extensive host emission band along with characteristic Dy3+ emission peaks. Ab-initio theoretical studies suggested that partial energy transfer to Dy3+ could be ascribed to contribution of Dy 4f orbitals to valence band predominantly formed by O 2p orbitals which enhances the probability of back transfer. Time resolved studies yielded single lifetimes for Eu3+ and Tb3+ but two lifetimes for Dy3+. The fact that the lifetime for excited states of Dy3+ was ∼10 times lesser than Eu3+ and Tb3+ also supported the existence of alternate pathways for the excited state of Dy3+. Various photophysical parameters were determined for GdScO3:Eu composition. Co-doping of all the three activators (Eu, Tb and Dy) led to a near white light emission suggesting its applicability as white-light and muticolored phosphors.