Enhancement in Luminescence of Lanthanide Metal Complex on addition of Fluorescent Carbon dots

Abstract

Highly fluorescent Lanthanide metal complexes have shown great potential application in the optics area. However, the insufficient luminescence of lanthanide complexes remains the potential bottleneck. Earlier, on addition of organic light harvesting molecule an enhancement in fluorescent quantum yield of the lanthanide complexes were perceived, although it was inadequate for practical applications. Herein, we have synthesized TbIII2(L)2(NO3)2(dmf)2 complex, using a ligand obtained by 1:1 condensation of salicylaldehyde and 2-(2-Aminoethoxy)ethanol, H2L. Photoluminescence study revealed pure green light emission from the TbIIIL-complex with the QY of ̴3.37%. The fluorescent emission was further enhanced on combining TbIIIL with N, S-Doped carbon dots (CDs), derived from Sulphilinamide and Citric acid. Almost six-fold increase in photoluminescence quantum yield from 3.37% to 21%. The enhancement was rationalized by the energy harvesting capacity of the CDs with consecutive transfer of the energy to the excited level of the luminescent TbIII metal centres. This phenomena have been reversed on addition of luminescent TbIIIL to the fluorescent CD solution, supporting indeed an energy transfer from CDs → TbIIIL. Herein, a simple and easy strategy was conveyed to improve the quantum yield of the lanthanide complexes on incorporation of CDs to be implemented for optical, sensing and anti-counterfeiting applications.