Lanthanide induced formation of novel luminescent alginate hydrogels and detection features

Responsive photo-luminescent soft matters have led to the design of optical sensors and switches. In this research, two new organic-inorganic type hybrid hydrogels have been fabricated by the self-assembly of sodium alginate and lanthanide elements. The incorporation of europium ions (Eu3+) (or terbium ions (Tb3+)) was required for the gelation of the dissolved alginate and thermally stable gels were formed. It has been found that red/green emissions derived from lanthanide ions were clearly identified in pure aqueous media through the metal coordination interactions with assembled alginate. These supramolecular structures could partially prevent the Eu3+ (or Tb3+) from being attacked by high frequency vibrations. More importantly, the lanthanide luminescence could be switched “off-on” in the presence of the anthrax biomarker sodium dipicolinate (NaDPA). The detection limits (for NaDPA) were determined to be 8.3 × 10−8 M and 9.0 × 10−8 M based on Eu(III) and Tb(III) gel, respectively.