Luminescence_information

Luminescence (definition): Luminescent materials are compounds that emit light, mostly in the visible and near infrared (NIR)

regions, through the conversion of the excitation energy into an electromagnetic radiation.

How does phosphorescence got its name?

It is interesting to note that several luminescent compounds were misleadingly named; for example, white phosphorous - from which the term “phosphorescence” originally derived, does not actually exhibit phosphorescence, its ability to exhibit green glow in the dark upon exposure to oxygen is due to a chemiluminescent mechanism.

Important characteristics for luminescent materials

(a) quantum yield (phi)

(b) molar absorptivity (ɛ) (also called molar extinction coefficient)

(c) luminescence lifetime (τ)

(d) Stokes shift

(ref: Photoluminescent, Upconversion Luminescent and Nonlinear Optical Metal-organic Frameworks: From Fundamental Photophysics to Potential Applications)

What is so Unique about RE (Nd3+) for Biomedical Applications?

(a) Large Stoke’s shift (~500nm) & strong emission

(b) Multi-frequency absorption & emission

(c) Long fluorescence lifetimes

(d) Optical properties “independent” of size

(e) Nontoxic

Lanthanide transitions:

a) The fluorescence decay time is ~ 133.89 us. This is consistent with the decay time of Er+3 in other up-conversion materials (Ref: ACS Appl. Mater. Interfaces 2016, 8, 17389-17394; Adv. Funct. Mater. 2009, 19, 2924-2929).