Infrared to visible upconversion luminescent materials for imaging applications

Abstract

newlineOver the past years the research on luminescent materials are getting newlinemuch attention with new materials, processes and applications. newlineUpconversion luminescence is the emission of a high energy photon by a newlinematerial on exciting with a low energy photon. It is an anti Stoke, multi newlinephoton process in which sequential absorption of photon will occur. newlineUpconversion process is much efficient process compared to other newlinemultiphoton processes. Due to the real intermediate energy level and newlinehigher excited state lifetime, upconversion process requires only much newlinelower excitation intensity that allows the use of inexpensive continuous newlinewave diode lasers against expensive femtosecond pulsed lasers needed for newlinesimultaneous two-photon excitation. Generally, upconversion newlineluminescence is achieved by doping a host material with suitable rare newlineearth ions. Emission of multiple and narrow emission lines is a property newlineof this kind of materials. The properties of host materials and the newlineincorporation of dopant (sensitizer and activator) ions within the host newlinecrystal lattice have a significant influence on the upconversion process. newlineThe lattice of host material will determine the distribution of dopant ion newlineand the distance between them. The local structure around dopant ions is newlinedifferent in different host materials. Therefore, the selection of suitable newlinehost material is essential for achieving upconversion luminescent material newlinewith the desired optical properties like colour tunability and luminescence newlineefficiency. Upconversion luminescent nanoparticles recently attract good newlineresearch interest because of its potential for light-harvesting properties in newlinesolar cells and for photocatalysis, optical manipulation in many fields like bioimaging, temperature sensor, chemical sensor, etc. and its properties newlinelike colour tunability for security printing. In this work, erbium (activator newlineion), ytterbium (sensitizer ion) co-doped upconversion luminescent newlinematerials were developed for cell imaging applications.